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In [[biochemistry]], '''P<sub>50</sub>''' indicates the [[partial pressure]] of a [[gas]] required to achieve 50% [[enzyme]] saturation.<ref>[http://medical-dictionary.thefreedictionary.com/P+50 P 50 – definition of P 50 in the Medical dictionary – by the Free Online Medical Dictionary, Thesaurus and Encyclopedia]. Medical-dictionary.thefreedictionary.com. Retrieved on 2013-10-22.</ref><ref>[http://www.lexingtonpulmonary.com/education/oxyhb/oxyhb.html Oxygen/Hemoglobin]. Lexingtonpulmonary.com. Retrieved on 2013-10-22.</ref> Values of P<sub>50</sub> are negatively correlated with substrate affinity, with lower values of P<sub>50</sub> corresponding to high affinity and ''vice versa''. The term is analogous to the [[Michaelis-Menten constant]] (K<sub>m</sub>), which identifies the [[concentration]] of substrate required for an enzyme to achieve 50% of its maximum [[enzyme reaction rate|reaction velocity]].
In [[biochemistry]], '''P<sub>50</sub>''' indicates the [[partial pressure]] of a [[gas]] required to achieve 50% [[enzyme]] saturation.<ref>[http://medical-dictionary.thefreedictionary.com/P+50 P 50 – definition of P 50 in the Medical dictionary – by the Free Online Medical Dictionary, Thesaurus and Encyclopedia]. Medical-dictionary.thefreedictionary.com. Retrieved on 2013-10-22.</ref><ref>[http://www.lexingtonpulmonary.com/education/oxyhb/oxyhb.html Oxygen/Hemoglobin]. Lexingtonpulmonary.com. Retrieved on 2013-10-22.</ref> Values of P<sub>50</sub> are negatively correlated with substrate affinity, with lower values of P<sub>50</sub> corresponding to high affinity and ''vice versa''. The term is analogous to the [[Michaelis-Menten constant]] (K<sub>m</sub>), which identifies the [[concentration]] of substrate required for an enzyme to achieve 50% of its maximum [[enzyme reaction rate|reaction velocity]].


For example, the P<sub>50</sub> of [[myoglobin]] for [[oxygen|O<sub>2</sub>]] is 130 [[pascal (unit)|pascal]]s while the P<sub>50</sub> for [[hemoglobin|adult hemoglobin]] is 3.5 kPa. Thus, when O<sub>2</sub> partial pressure is low, hemoglobin-bound O<sub>2</sub> is more readily transferred to myoglobin. Myoglobin, found in high concentrations in [[muscle]] tissue, can then transfer the oxygen to [[muscle fiber]]s, where it will be used in the generation of energy to fuel muscle contraction.<ref>{{cite journal|pmid=2706089 | volume=11 | issue=1 | title=Modification of partial pressure of oxygen (P50) in mammalian red blood cells by incorporation of an allosteric effector of hemoglobin | year=2001| journal=Biotechnol. Appl. Biochem. | pages=31–40|last1=Bailleul|first1=C|last2=Borrelly-Villereal|first2=MC|last3=Chassaigne|first3=M|last4=Ropars|first4=C}}</ref>
For example, the P<sub>50</sub> of [[myoglobin]] for [[oxygen|O<sub>2</sub>]] is 130 [[pascal (unit)|pascal]]s while the P<sub>50</sub> for [[hemoglobin|adult hemoglobin]] is 3.5 kPa. Thus, when O<sub>2</sub> partial pressure is low, hemoglobin-bound O<sub>2</sub> is more readily transferred to myoglobin. Myoglobin, found in high concentrations in [[muscle]] tissue, can then transfer the oxygen to muscle tissue[[muscle fiber]]s, where it will be used in the generation of energy to fuel muscle contraction.<ref>{{cite journal|pmid=2706089 | volume=11 | issue=1 | title=Modification of partial pressure of oxygen (P50) in mammalian red blood cells by incorporation of an allosteric effector of hemoglobin | year=2001| journal=Biotechnol. Appl. Biochem. | pages=31–40|last1=Bailleul|first1=C|last2=Borrelly-Villereal|first2=MC|last3=Chassaigne|first3=M|last4=Ropars|first4=C}}</ref>


==References==
==References==

Revision as of 08:26, 17 February 2017

In biochemistry, P50 indicates the partial pressure of a gas required to achieve 50% enzyme saturation.[1][2] Values of P50 are negatively correlated with substrate affinity, with lower values of P50 corresponding to high affinity and vice versa. The term is analogous to the Michaelis-Menten constant (Km), which identifies the concentration of substrate required for an enzyme to achieve 50% of its maximum reaction velocity.

For example, the P50 of myoglobin for O2 is 130 pascals while the P50 for adult hemoglobin is 3.5 kPa. Thus, when O2 partial pressure is low, hemoglobin-bound O2 is more readily transferred to myoglobin. Myoglobin, found in high concentrations in muscle tissue, can then transfer the oxygen to muscle tissuemuscle fibers, where it will be used in the generation of energy to fuel muscle contraction.[3]

References

  1. ^ P 50 – definition of P 50 in the Medical dictionary – by the Free Online Medical Dictionary, Thesaurus and Encyclopedia. Medical-dictionary.thefreedictionary.com. Retrieved on 2013-10-22.
  2. ^ Oxygen/Hemoglobin. Lexingtonpulmonary.com. Retrieved on 2013-10-22.
  3. ^ Bailleul, C; Borrelly-Villereal, MC; Chassaigne, M; Ropars, C (2001). "Modification of partial pressure of oxygen (P50) in mammalian red blood cells by incorporation of an allosteric effector of hemoglobin". Biotechnol. Appl. Biochem. 11 (1): 31–40. PMID 2706089.