Work

Inverse enzyme isotope effects in human purine nucleoside phosphorylase with heavy asparagine labels

Year: 2018

Type: article

Abstract: = 0.71). Substrate-trapping experiments provided independent confirmation of improved catalysis in these constructs. Transition path-sampling analysis of these partially labeled PNPs indicate altered femtosecond catalytic site motions with improved Asn243 interactions to the purine leaving group. Altered transition state barrier recrossing has been proposed as an explanation for heavy-PNP isotope effects but is incompatible with these isotope effects. Rate-limiting product release governs steady-state kinetics in this enzyme, and kinetic constants were unaffected in the labeled PNPs. The study suggests that mass-constrained femtosecond motions at the catalytic site of PNP can improve transition state barrier crossing by more frequent sampling of essential catalytic site contacts.

Source: Proceedings of the National Academy of Sciences

DOI: 10.1073/pnas.1805416115

Authors: Rajesh K. Harijan, Ioanna Zoi, Dimitri Antoniou, Steven D. Schwartz, Vern L. Schramm

Institutions: Albert Einstein College of Medicine, University of Arizona

Language: English

Topic: Biochemical and Molecular Research

Subfield: Molecular Biology

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

Open Access status: green

Funders: National Institutes of Health, National Institute of General Medical Sciences

Awards: Transition State Analysis of Enzymatic Reactions, Protein Dynamics in Enzymatic Catalysis, Transition State Analysis of Enzymatic Reactions, G3981344285, G9000234506