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{{Infobox enzyme |
{{Infobox enzyme |
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| Name = Molybdopterin synthase |
| Name = Molybdopterin synthase |
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| EC_number = 2.8.1.12 |
| EC_number = 2.8.1.12 |
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| IUBMB_EC_number = 2/8/1/12 |
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'''Molybdopterin synthase''' ({{EC number|2.8.1.12}}, ''MPT synthase'') is an [[enzyme]] required to synthesize [[ |
'''Molybdopterin synthase''' ({{EC number|2.8.1.12}}, '''MPT synthase''') is an [[enzyme]] required to synthesize [[molybdopterin]] (MPT) from precursor Z (now known as [[cyclic pyranopterin monophosphate]]).<ref name=":6">{{cite journal | vauthors = Daniels JN, Wuebbens MM, Rajagopalan KV, Schindelin H | title = Crystal structure of a molybdopterin synthase-precursor Z complex: insight into its sulfur transfer mechanism and its role in molybdenum cofactor deficiency | journal = Biochemistry | volume = 47 | issue = 2 | pages = 615–26 | date = January 2008 | pmid = 18092812 | doi = 10.1021/bi701734g }}</ref><ref>{{cite journal | vauthors = Wuebbens MM, Rajagopalan KV | title = Mechanistic and mutational studies of Escherichia coli molybdopterin synthase clarify the final step of molybdopterin biosynthesis | journal = The Journal of Biological Chemistry | volume = 278 | issue = 16 | pages = 14523–32 | date = April 2003 | pmid = 12571226 | doi = 10.1074/jbc.m300453200 | doi-access = free }}</ref> Molydopterin is subsequently [[Complex (chemistry)|complexed]] with [[molybdenum]] to form molybdenum cofactor (MoCo). MPT synthase [[catalysis|catalyses]] the following [[chemical reaction]]: |
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:[[cyclic pyranopterin monophosphate|precursor Z]] + 2 [molybdopterin-synthase sulfur-carrier protein]-Gly-NH-CH<sub>2</sub>-C(O)SH + H<sub>2</sub>O <math>\rightleftharpoons</math> |
:[[cyclic pyranopterin monophosphate|precursor Z]] + 2 [molybdopterin-synthase sulfur-carrier protein]-Gly-NH-CH<sub>2</sub>-C(O)SH + H<sub>2</sub>O <math>\rightleftharpoons</math> molybdopterin + 2 molybdopterin-synthase sulfur-carrier protein |
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Molybdopterin synthase is [[heterodimeric]] and coded for by the [[MOCS2]] gene.<ref>{{cite journal | vauthors = Sloan J, Kinghorn JR, Unkles SE | title = The two subunits of human molybdopterin synthase: evidence for a bicistronic messenger RNA with overlapping reading frames | journal = Nucleic Acids Research | volume = 27 | issue = 3 | pages = 854–8 | date = February 1999 | pmid = 9889283 | pmc = 148257 | doi = 10.1093/nar/27.3.854 }}</ref> Genetic deficiencies of enzymes such as MPT synthase, which are involved in MoCo [[biosynthesis]], lead to [[Molybdenum cofactor deficiency|MoCo deficiency]], a rare disease that results in severe neurological abnormalities.<ref name=":0">{{Cite journal|last=Rudolph, Michael J. and Wuebbens, Margot M. and Rajagopalan, K. V. and Schindelin, Hermann|date=2001|title=Crystal structure of molybdopterin synthase and its evolutionary relationship to ubiquitin activation|journal=Nature Structural Biology|volume=8|issue=1|pages=42–46|doi=10.1038/83034|pmid=11135669|s2cid=10494830}}</ref><ref name=":1">{{Cite journal|last=Silke Leimkühler, Andrea Freuer, Jose ́ Angel Santamaria Araujo, K. V. Rajagopalan, and Ralf R. Mendel|date=2003|title=Mechanistic Studies of Human Molybdopterin Synthase Reaction and Characterization of Mutants Identified in Group B Patients of Molybdenum Cofactor Deficiency|journal=Journal of Biological Chemistry|volume=278|issue=28|pages=26127–26134|doi=10.1074/jbc.M303092200|pmid=12732628|doi-access=free}}</ref><ref name=":2">{{Cite journal|last=Stallmeyer, B., Schwarz, G., Schulze, J., Nerlich, A., Reiss, J., Kirsch, J., Mendel, R. R.|date=1999|title=The neurotransmitter receptor-anchoring protein gephyrin reconstitutes molybdenum cofactor biosynthesis in bacteria, plants, and mammalian cells|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=96|issue=4|pages=1333–1338|pmc=15463|pmid=9990024|doi=10.1073/pnas.96.4.1333|bibcode=1999PNAS...96.1333S |doi-access=free}}</ref><ref name=":3">{{Cite journal|last=Reiss J|date=2000|title=Genetics of molybdenum cofactor deficiency|journal=Human Genetics|volume=106|issue=2|pages=157–163|pmid=10746556|doi=10.1007/s004390051023|doi-broken-date=2024-11-02 }}</ref> |
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| ⚫ | The high resolution [[crystal structure]] of MPT synthase shows the enzyme has a [[Heterotetramer|heterotetrametric]] structure composed of two small subunits (MoaD in [[prokaryotes]]) and two large subunits (MoaE in prokaryotes) with the small subunits at opposite ends of a central large subunit [[Dimer (chemistry)|dimer]].<ref name=":6" /><ref name=":0" /><ref name=":1" /> The C-terminus of each small subunit is inserted into a large subunit to form the [[active site]].<ref name=":0" /> In the enzyme's activated form the C-terminus is present as a [[Thiocarboxylic acid|thiocarboxylate]], which acts as the [[sulfur]] donor to precursor Z in MoCo [[biosynthesis]].<ref name=":0" /> As a result, the active site of the enzyme must be in close proximity to the C-terminus of the small subunit (i.e. MoaD in prokaryotes). The high resolution [[crystal structure]] of the enzyme also reveals the presence of a binding pocket for the terminal [[phosphate]] of molybdopterin and suggests a possible binding site for the [[pterin]] [[Moiety (chemistry)|moiety]] present both in precursor Z and molybdopterin.<ref name=":7">{{Cite journal|last=Michael J. Rudolph, Margot M. Wuebbens, Oliver Turque, K. V. Rajagopalan, Hermann Schindelin|date=2003|title=Structural Studies of Molybdopterin Synthase Provide Insights into Its Catalytic Mechanism|journal=Journal of Biological Chemistry|volume=278|issue=16|pages=14514–14522|doi=10.1074/jbc.M300449200|pmid=12571227|doi-access=free}}</ref> |
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| ⚫ | The structural similarity between [[ubiquitin]] and the small subunit of MPT synthase hints at the evolutionary relationship of the MoCo [[biosynthesis]] pathway and the ubiquitin dependent [[protein degradation]] pathway.<ref name=":0" /><ref name=":8">{{Cite journal|last=Wang, Chunyu and Xi, Jun and Begley, Tadhg P. and Nicholson, Linda K.|date=2001|title=Solution structure of ThiS and implications for the evolutionary roots of ubiquitin|url=https://www.nature.com/articles/nsb0101_47|journal=Nature Structural and Molecular Biology|volume=8|issue=1|pages=47–51|doi=10.1038/83041|pmid=11135670|s2cid=29632248}}</ref> Specifically, the small subunit MoaD in prokaryotes is a [[Sequence homology|sequence homolog]] of [[URM1|Urm1]], indicating that ''MPT synthase'' probably shares a [[common ancestor]] with ubiquitin.<ref name=":8" /> |
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| ⚫ | The high resolution [[ |
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| ⚫ | The structural similarity between [[ubiquitin]] and the small subunit of |
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| ⚫ | The [[biosynthesis]] of MoCo is an old and evolutionary conserved pathway present in [[eukaryote]]s, [[eubacteria]], and [[Archaea|archea]], which can be divided into three major steps.<ref name=":0" /> The first step involves the conversion of a [[guanosine]] [[nucleotide]] into precursor Z.<ref name=":0" /><ref name=":4">{{Cite journal|last=Margot M. Wuebbens, K. V. Rajagopalan|date=1995|title=Investigation of the Early Steps of Molybdopterin Biosynthesis in Escherichia coli through the Use of in Vivo Labeling Studies|journal=Journal of Biological Chemistry|volume=270|issue=3|pages=1082–1087|doi=10.1074/jbc.270.3.1082|pmid=7836363|doi-access=free}}</ref> In the following step, MPT synthase [[Catalysis|catalyzes]] the incorporation of the [[dithiolene]] moiety to precursor Z, which converts it to molybdopterin.<ref name=":0" /> More specifically, this interconversion involves the opening of the cyclic phosphate ring of precursor Z, and the addition of two side chain [[sulfhydryl group]]s.<ref name=":4" /> [[Escherichia coli|E-coli]] ''MPT synthase'' is activated by the formation of a [[Thiocarboxylic acid|thiocarboxylate]] group at the second [[glycine]] of its [[C-terminus|C-terminal]] Gly-Gly motif, which serves as the [[sulfur]] donor for the formation of the diothiolene group in MPT.<ref name=":1" /><ref>{{Cite journal|last=Gerrit Gutzke, Berthold Fischer, Ralf R. Mendel, Günter Schwarz|date=2001|title=Thiocarboxylation of Molybdopterin Synthase Provides Evidence for the Mechanism of Dithiolene Formation in Metal-binding Pterins|journal=Journal of Biological Chemistry|volume=276|issue=39|pages=36268–36274|doi=10.1074/jbc.M105321200|pmid=11459846|doi-access=free}}</ref> That is, the mechanism on ''MPT synthase'' depends on the interconversion between the activated form of MoaD with the [[Thiocarboxylic acid|thiocarboxylate]] group and the MoaE protein<ref name=":7" /> In the final step of MoCo [[biosynthesis]], [[Molybdenum|molybendum]] is incorporated to [[Molybdopterin|MPT]] by the two-domain [[protein]] [[gephyrin]].<ref name=":1" /><ref name=":2" /> MPT synthase sulfurylase recharges MPT synthase with a sulfur atom after each catalytic cycle.<ref name=":8" /> |
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| ⚫ | MPT synthase is involved in the [[biosynthesis]] of MoCo, which is essential for the activity of enzymes like [[xanthine dehydrogenase]], [[aldehyde oxidase]], and [[sulfite oxidase]] in humans.<ref name=":1" /> MoCo containing enzymes typically catalyze the net transfer of an [[oxygen]] [[atom]] to and from their [[Substrate (chemistry)|substrates]] in a two [[electron]] [[redox reaction]].<ref name=":0" /> |
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| ⚫ | The [[biosynthesis]] of |
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| ⚫ | [[Molybdenum cofactor deficiency|MoCo deficiency]] in humans results in the combined deficiency of the MoCo-containing enzymes: [[sulfite oxidase]], [[xanthine oxidase]], and [[aldehyde oxidase]].<ref name=":0" /><ref name=":1" /><ref name=":3" /> Symptoms of MoCo deficiency are linked to the accumulation of toxic [[metabolite]]s caused by the reduced activity of these molybdoenzymes, especially sulfite oxidase.<ref name=":0" /> [[Genetic defects]] in MoCo [[biosynthesis]] lead to MoCo deficiency.<ref name=":0" /> These genetic defects affect the formation of precursor Z (known as group A MoCo deficiency) or the conversion of precursor Z to MoCo by ''MPT synthase'' (known as group B MoCo deficiency).<ref name=":3" /><ref name=":5">{{Cite journal|last=J. Reiss, C. Dorche, B. Stallmeyer, R. R. Mendel, N. Cohen, M. T. Zabot|date=1999|title=Human Molybdopterin Synthase Gene: Genomic Structure and Mutations in Molybdenum Cofactor Deficiency Type B|journal=The American Journal of Human Genetics|volume=64|issue=3|pages=706–711|pmc=1377787|pmid=10053004|doi=10.1086/302296}}</ref> [[MOCS1]] is defective for group A (the majority of patients), and encodes two enzymes involved in the formation of precursor Z.<ref name=":3" /><ref name=":5" /> [[MOCS2]] is defective for group B and encodes the small and large subunits of ''MPT synthase''.<ref name=":3" /><ref name=":5" /> Groups A and B of deficiency show an identical [[phenotype]], characterized by [[neonatal seizure]]s, attenuated brain growth, dislocated ocular lenses, feeding difficulties, among other neurological symptoms.<ref name=":0" /><ref name=":1" /><ref name=":2" /><ref name=":3" /><ref name=":5" /> This rare but severe deficiency is an [[Autosome|autosomal]] [[Dominance (genetics)|recessive trait]], which usually results in early childhood death as there is currently no available treatment.<ref name=":0" /><ref name=":1" /><ref name=":2" /><ref name=":3" /> |
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| ⚫ | [[Molybdenum cofactor deficiency|MoCo deficiency]] in humans results in the combined deficiency of the |
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== References == |
== References == |
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{{Sulfur-containing group transferases}} |
{{Sulfur-containing group transferases}} |
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{{biochem-stub}} |
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[[Category:EC 2.8.1]] |
[[Category:EC 2.8.1]] |
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Latest revision as of 11:31, 2 November 2024
| Molybdopterin synthase | |||||||||
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| Identifiers | |||||||||
| EC no. | 2.8.1.12 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
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Molybdopterin synthase (EC 2.8.1.12, MPT synthase) is an enzyme required to synthesize molybdopterin (MPT) from precursor Z (now known as cyclic pyranopterin monophosphate).[1][2] Molydopterin is subsequently complexed with molybdenum to form molybdenum cofactor (MoCo). MPT synthase catalyses the following chemical reaction:
- precursor Z + 2 [molybdopterin-synthase sulfur-carrier protein]-Gly-NH-CH2-C(O)SH + H2O molybdopterin + 2 molybdopterin-synthase sulfur-carrier protein
Molybdopterin synthase is heterodimeric and coded for by the MOCS2 gene.[3] Genetic deficiencies of enzymes such as MPT synthase, which are involved in MoCo biosynthesis, lead to MoCo deficiency, a rare disease that results in severe neurological abnormalities.[4][5][6][7]
Structure
[edit]
The high resolution crystal structure of MPT synthase shows the enzyme has a heterotetrametric structure composed of two small subunits (MoaD in prokaryotes) and two large subunits (MoaE in prokaryotes) with the small subunits at opposite ends of a central large subunit dimer.[1][4][5] The C-terminus of each small subunit is inserted into a large subunit to form the active site.[4] In the enzyme's activated form the C-terminus is present as a thiocarboxylate, which acts as the sulfur donor to precursor Z in MoCo biosynthesis.[4] As a result, the active site of the enzyme must be in close proximity to the C-terminus of the small subunit (i.e. MoaD in prokaryotes). The high resolution crystal structure of the enzyme also reveals the presence of a binding pocket for the terminal phosphate of molybdopterin and suggests a possible binding site for the pterin moiety present both in precursor Z and molybdopterin.[8]
The structural similarity between ubiquitin and the small subunit of MPT synthase hints at the evolutionary relationship of the MoCo biosynthesis pathway and the ubiquitin dependent protein degradation pathway.[4][9] Specifically, the small subunit MoaD in prokaryotes is a sequence homolog of Urm1, indicating that MPT synthase probably shares a common ancestor with ubiquitin.[9]
Mechanism
[edit]
The biosynthesis of MoCo is an old and evolutionary conserved pathway present in eukaryotes, eubacteria, and archea, which can be divided into three major steps.[4] The first step involves the conversion of a guanosine nucleotide into precursor Z.[4][10] In the following step, MPT synthase catalyzes the incorporation of the dithiolene moiety to precursor Z, which converts it to molybdopterin.[4] More specifically, this interconversion involves the opening of the cyclic phosphate ring of precursor Z, and the addition of two side chain sulfhydryl groups.[10] E-coli MPT synthase is activated by the formation of a thiocarboxylate group at the second glycine of its C-terminal Gly-Gly motif, which serves as the sulfur donor for the formation of the diothiolene group in MPT.[5][11] That is, the mechanism on MPT synthase depends on the interconversion between the activated form of MoaD with the thiocarboxylate group and the MoaE protein[8] In the final step of MoCo biosynthesis, molybendum is incorporated to MPT by the two-domain protein gephyrin.[5][6] MPT synthase sulfurylase recharges MPT synthase with a sulfur atom after each catalytic cycle.[9]
Biological function
[edit]MPT synthase is involved in the biosynthesis of MoCo, which is essential for the activity of enzymes like xanthine dehydrogenase, aldehyde oxidase, and sulfite oxidase in humans.[5] MoCo containing enzymes typically catalyze the net transfer of an oxygen atom to and from their substrates in a two electron redox reaction.[4]
Disease relevance
[edit]MoCo deficiency in humans results in the combined deficiency of the MoCo-containing enzymes: sulfite oxidase, xanthine oxidase, and aldehyde oxidase.[4][5][7] Symptoms of MoCo deficiency are linked to the accumulation of toxic metabolites caused by the reduced activity of these molybdoenzymes, especially sulfite oxidase.[4] Genetic defects in MoCo biosynthesis lead to MoCo deficiency.[4] These genetic defects affect the formation of precursor Z (known as group A MoCo deficiency) or the conversion of precursor Z to MoCo by MPT synthase (known as group B MoCo deficiency).[7][12] MOCS1 is defective for group A (the majority of patients), and encodes two enzymes involved in the formation of precursor Z.[7][12] MOCS2 is defective for group B and encodes the small and large subunits of MPT synthase.[7][12] Groups A and B of deficiency show an identical phenotype, characterized by neonatal seizures, attenuated brain growth, dislocated ocular lenses, feeding difficulties, among other neurological symptoms.[4][5][6][7][12] This rare but severe deficiency is an autosomal recessive trait, which usually results in early childhood death as there is currently no available treatment.[4][5][6][7]
References
[edit]- ^ a b Daniels JN, Wuebbens MM, Rajagopalan KV, Schindelin H (January 2008). "Crystal structure of a molybdopterin synthase-precursor Z complex: insight into its sulfur transfer mechanism and its role in molybdenum cofactor deficiency". Biochemistry. 47 (2): 615–26. doi:10.1021/bi701734g. PMID 18092812.
- ^ Wuebbens MM, Rajagopalan KV (April 2003). "Mechanistic and mutational studies of Escherichia coli molybdopterin synthase clarify the final step of molybdopterin biosynthesis". The Journal of Biological Chemistry. 278 (16): 14523–32. doi:10.1074/jbc.m300453200. PMID 12571226.
- ^ Sloan J, Kinghorn JR, Unkles SE (February 1999). "The two subunits of human molybdopterin synthase: evidence for a bicistronic messenger RNA with overlapping reading frames". Nucleic Acids Research. 27 (3): 854–8. doi:10.1093/nar/27.3.854. PMC 148257. PMID 9889283.
- ^ a b c d e f g h i j k l m n Rudolph, Michael J. and Wuebbens, Margot M. and Rajagopalan, K. V. and Schindelin, Hermann (2001). "Crystal structure of molybdopterin synthase and its evolutionary relationship to ubiquitin activation". Nature Structural Biology. 8 (1): 42–46. doi:10.1038/83034. PMID 11135669. S2CID 10494830.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ a b c d e f g h Silke Leimkühler, Andrea Freuer, Jose ́ Angel Santamaria Araujo, K. V. Rajagopalan, and Ralf R. Mendel (2003). "Mechanistic Studies of Human Molybdopterin Synthase Reaction and Characterization of Mutants Identified in Group B Patients of Molybdenum Cofactor Deficiency". Journal of Biological Chemistry. 278 (28): 26127–26134. doi:10.1074/jbc.M303092200. PMID 12732628.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ a b c d Stallmeyer, B., Schwarz, G., Schulze, J., Nerlich, A., Reiss, J., Kirsch, J., Mendel, R. R. (1999). "The neurotransmitter receptor-anchoring protein gephyrin reconstitutes molybdenum cofactor biosynthesis in bacteria, plants, and mammalian cells". Proceedings of the National Academy of Sciences of the United States of America. 96 (4): 1333–1338. Bibcode:1999PNAS...96.1333S. doi:10.1073/pnas.96.4.1333. PMC 15463. PMID 9990024.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ a b c d e f g Reiss J (2000). "Genetics of molybdenum cofactor deficiency". Human Genetics. 106 (2): 157–163. doi:10.1007/s004390051023 (inactive 2024-11-02). PMID 10746556.
{{cite journal}}: CS1 maint: DOI inactive as of November 2024 (link) - ^ a b Michael J. Rudolph, Margot M. Wuebbens, Oliver Turque, K. V. Rajagopalan, Hermann Schindelin (2003). "Structural Studies of Molybdopterin Synthase Provide Insights into Its Catalytic Mechanism". Journal of Biological Chemistry. 278 (16): 14514–14522. doi:10.1074/jbc.M300449200. PMID 12571227.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ a b c Wang, Chunyu and Xi, Jun and Begley, Tadhg P. and Nicholson, Linda K. (2001). "Solution structure of ThiS and implications for the evolutionary roots of ubiquitin". Nature Structural and Molecular Biology. 8 (1): 47–51. doi:10.1038/83041. PMID 11135670. S2CID 29632248.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ a b Margot M. Wuebbens, K. V. Rajagopalan (1995). "Investigation of the Early Steps of Molybdopterin Biosynthesis in Escherichia coli through the Use of in Vivo Labeling Studies". Journal of Biological Chemistry. 270 (3): 1082–1087. doi:10.1074/jbc.270.3.1082. PMID 7836363.
- ^ Gerrit Gutzke, Berthold Fischer, Ralf R. Mendel, Günter Schwarz (2001). "Thiocarboxylation of Molybdopterin Synthase Provides Evidence for the Mechanism of Dithiolene Formation in Metal-binding Pterins". Journal of Biological Chemistry. 276 (39): 36268–36274. doi:10.1074/jbc.M105321200. PMID 11459846.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ a b c d J. Reiss, C. Dorche, B. Stallmeyer, R. R. Mendel, N. Cohen, M. T. Zabot (1999). "Human Molybdopterin Synthase Gene: Genomic Structure and Mutations in Molybdenum Cofactor Deficiency Type B". The American Journal of Human Genetics. 64 (3): 706–711. doi:10.1086/302296. PMC 1377787. PMID 10053004.
{{cite journal}}: CS1 maint: multiple names: authors list (link)