pKa of selenocysteine

Value 5.2 unitless
Organism Generic
Reference Axley MJ, Böck A, Stadtman TC. Catalytic properties of an Escherichia coli formate dehydrogenase mutant in which sulfur replaces selenium. Proc Natl Acad Sci U S A. 1991 Oct 188(19):8450-4.PubMed ID1924303
Comments While the selenol of free selenocysteine has a pKa of 5.2, the thiol of free cysteine has a pKa greater than 8. Therefore, at physiological pH values a selenol group is almost fully ionized, while a thiol group is largely protonated.
Entered by Uri M
ID 102619