Premium
Distinct biochemical properties of human serine hydroxymethyltransferase compared with the P lasmodium enzyme: implications for selective inhibition
Author(s) -
Pinthong Chatchadaporn,
Maenpuen Somchart,
Amornwatcharapong Watcharee,
Yuthavong Yongyuth,
Leartsakulpanich Ubolsree,
Chaiyen Pimchai
Publication year - 2014
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.12803
Subject(s) - serine hydroxymethyltransferase , serine , enzyme , chemistry , glycine , substrate (aquarium) , biochemistry , stereochemistry , biology , amino acid , ecology
Serine hydroxymethyltransferase ( SHMT ) catalyzes the transfer of a hydroxymethyl group from l ‐serine to tetrahydrofolate to yield glycine and 5,10‐methylenetetrahydrofolate. Our previous investigations have shown that SHMT s from P lasmodium spp. ( P . falciparum , Pf; P . vivax , Pv) are different from the enzyme from rabbit liver in that P lasmodium SHMT can use d ‐serine as a substrate. In this report, the biochemical and biophysical properties of the P lasmodium and the human cytosolic form (hc SHMT ) enzymes including ligand binding and kinetics were investigated. The data indicate that, similar to P lasmodium enzymes, hc SHMT can use d ‐serine as a substrate. However, hc SHMT displays many properties that are different from those of the Plasmodium enzymes. The molar absorption coefficient of hc SHMT ‐bound pyridoxal‐5′‐phosphate ( PLP ) is much greater than Pv SHMT ‐bound or Pf SHMT ‐bound PLP . The binding interactions of hc SHMT and P lasmodium SHMT with d ‐serine are different, as only the P lasmodium enzyme undergoes formation of a quinonoid‐like species upon binding to d ‐serine. Furthermore, it has been noted that hc SHMT displays strong substrate inhibition by tetrahydrofolate ( THF ) (at THF > 40 μ m ), compared with SHMT s from Plasmodium and other species. The pH–activity profile of hc SHMT shows higher activities at lower pH values corresponding to a p K a value of 7.8 ± 0.1. Thiosemicarbazide reacts with hc SHMT following a one‐step model [ k 1 of 12 ± 0.6 m −1 ·s −1 and k −1 of (1.0 ± 0.6) × 10 −3 s −1 ], while the same reaction with Pf SHMT involves at least three steps. All data indicated that the ligand binding environment of SHMT from human and Plasmodium are different, indicating that it should be possible to develop species‐selective inhibitors in future studies. Database serine hydroxymethyltransferase, EC 2.1.2.1 ; 5,10‐methylenetetrahydrofolate dehydrogenase, EC 1.5.1.5