Related Experiment Video
Updated: Aug 14, 2026

The Importance of Correct Protein Concentration for Kinetics and Affinity Determination in Structure-function Analysis
Published on: March 17, 2010
Determinants of cysteine pKa values in creatine kinase and alpha1-antitrypsin
1Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, USA.
Abstract:
The structural determinants of the unusually low pK(a) values of Cys282 in human creatine kinase and Cys232 in alpha1-antitrypsin were studied computationally. We have demonstrated that hydrogen bonding to the cysteine residue is the prime determinant for both proteins. In the case of creatine kinase, the hydrogen bond donors are a serine side chain and an amide NH-group, while in alpha1-antitrypsin the donor is an amide NH. Each hydrogen bond lowers the pK(a) by between 0.8 and 1.5 pH units. The 1.1-unit lowering due to the Ser284-Cys282 hydrogen bond is in good agreement with the 1.2-unit difference between the Cys282 pK(a) value of wild-type and the S284A mutant of creatine kinase.
Related Concept Videos
Acid and Bases: Ka, pKa, and Relative Strengths
Introduction to Mechanisms of Enzyme Catalysis
Allosteric Proteins-ATCase
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...
cAMP-dependent Protein Kinase Pathways
EDTA: Conditional Formation Constant
For the equilibrium reaction of the metal with the Y4− form of EDTA, the formation...
Drug Dosing in Renal Diseases: Measurement of Serum Creatinine Concentration and Clearance

