Bacterial versus human thymidylate synthase: Kinetics and functionality

Zahidul Islam; Ilya Gurevic; Timothy S Strutzenberg; Ananda K Ghosh; Tasnia Iqbal; Amnon Kohen

doi:10.1371/journal.pone.0196506

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Bacterial versus human thymidylate synthase: Kinetics and functionality

Journal article

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Peer reviewed

Bacterial versus human thymidylate synthase: Kinetics and functionality

Zahidul Islam, Ilya Gurevic, Timothy S Strutzenberg, Ananda K Ghosh, Tasnia Iqbal and Amnon Kohen

PloS one, Vol.13(5), pp.e0196506-e0196506

2018

DOI: 10.1371/journal.pone.0196506

PMCID: PMC5929524

PMID: 29715278

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Abstract

Thymidylate Synthase (TSase) is a highly conserved enzyme that catalyzes the production of the DNA building block thymidylate. Structurally, functionally and mechanistically, bacterial and mammalian TSases share remarkable similarities. Because of this closeness, bacterial enzymes have long been used as model systems for human TSase. Furthermore, while TSase inhibitors have long served as chemotherapeutic drugs, no TSase inhibitor serves as an antibiotic. Despite their high resemblance, the mammalian TSases are distinct in a few known aspects, such as having a N-terminal tail and two insertions in the primary sequence and active/inactive conformations. Here, we aim to comprehensively characterize human (hs) TSase and delineate its contrasts and the similarities to the well-studied Escherichia coli (ec) TSase. We found that, in contrast to ecTSase, Mg2+ does not enhance reaction rates for hsTSase. The temperature dependence of intrinsic kinetic isotope effects (KIEs), on the other hand, suggests that Mg2+ has little or no impact on the transition state of hydride transfer in either enzyme, and that the transition state for the hydride transfer in hsTSase is looser than in ecTSase. Additionally, the substrates' binding order is strictly ordered for ecTSase but slightly less ordered for hsTSase. The observed kinetic and functional differences between bacterial and human enzymes may aid in the development of antibiotic drugs with reduced toxicity.

Amino Acid Sequence

Escherichia coli - enzymology

Humans

Kinetics

Models, Molecular

Protein Conformation

Species Specificity

Thymidylate Synthase - chemistry

Thymidylate Synthase - metabolism

Details

Title: Subtitle: Bacterial versus human thymidylate synthase: Kinetics and functionality
Creators: Zahidul Islam - University of Iowa
Ilya Gurevic - University of Iowa
Timothy S Strutzenberg - University of Iowa
Ananda K Ghosh - University of Iowa
Tasnia Iqbal - University of Iowa
Amnon Kohen - University of Iowa
Resource Type: Journal article
Publication Details: PloS one, Vol.13(5), pp.e0196506-e0196506
DOI: 10.1371/journal.pone.0196506
PMID: 29715278
PMCID: PMC5929524
NLM abbreviation: PLoS One
ISSN: 1932-6203
eISSN: 1932-6203
Grant note: R01GM065368 / NIH HHS T32GM008365 / NIH HHS R01 GM065368 / NIGMS NIH HHS T32 GM008365 / NIGMS NIH HHS
Language: English
Date published: 2018
Academic Unit: Chemistry
Record Identifier: 9984230629402771

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