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Updated: Aug 14, 2026

The Importance of Correct Protein Concentration for Kinetics and Affinity Determination in Structure-function Analysis
Published on: March 18, 2010
Kinetic studies on Korean serum cis-AB enzymes reveal diminished A and B transferase activities
M H Yazer1, R B Zheng, N O L Seto
1The Institute for Transfusion Medicine and Department of Pathology, University of Pittsburgh, Pittsburgh, PA 15213, USA. myazer@itxm.org
Background:
cis-AB enzymes are rare glycosyltransferases that synthesize both blood group A and B antigens. We have identified a large cohort of Korean cis-AB blood donors and studied the N-acetylgalactosaminyltransferase (glycosyltransferase A, GTA) and galactosyltransferase (glycosyltransferase B, GTB) activity of their cis-AB serum enzymes.
Materials And Methods:
The cis-AB01 allele was identified by PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) in 60 donors collected at the Gwangju-Chonnam Red Cross Blood Center. Enzyme assays of this cis-AB enzyme were performed on available serum samples from 16 donors with the cis-AB01/O genotype and three with the cis-AB01/A genotype.
Results:
In cis-AB donors with an O allele, both the GTA and GTB activity of the cis-AB enzyme were markedly reduced compared to normal A and B controls (29% and 27%, respectively). This is consistent with the behaviour predicted from kinetic studies of a recombinant model of the corresponding AAAB enzyme.
Conclusion:
Although variable, cis-AB enzymes feature reduced GTA and GTB activities.
Summary:
Cis-AB enzymes feature variable but reduced GTA and GTB activities with relatively weaker GTB activity, consistent with the weak agglutination present on forward typing with anti-B.
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