Regulation of catalytic activity of a multifunctional polyketide biosynthetic enzyme, 6-hydroxymellein synthase, by interaction between NADPH and phenylglyoxal-sensitive amino acid residue at the reaction center
F. Kurosaki et al., Regulation of catalytic activity of a multifunctional polyketide biosynthetic enzyme, 6-hydroxymellein synthase, by interaction between NADPH and phenylglyoxal-sensitive amino acid residue at the reaction center, BBA-PROT ST, 1549(1), 2001, pp. 51-60
Citations number
30
Categorie Soggetti
Biochemistry & Biophysics
Journal title
BIOCHIMICA ET BIOPHYSICA ACTA-PROTEIN STRUCTURE AND MOLECULAR ENZYMOLOGY
Treatment of 6-hydroxymellein synthase, a multifunctional polyketide biosyn
thetic enzyme in carrot cells, with phenylglyoxal yielded a chemically modi
fied protein in which approximately two moles of the reagent were covalentl
y attached to each subunit of the enzyme. Only NADH- but not NADPH-associat
ed form of native 6-hydroxymellein synthase was inhibited by cerulenin; how
ever, the NADPH-synthase complex lost the insensitivity by the chemical mod
ification of the enzyme protein with phenylglyoxal. Appreciable differences
in K-m values observed between the NADPH- and NADH-associated enzymes were
greatly reduced by the treatment with phenylglyoxal. Although the catalyti
c activity of the NADPH-associated synthase was enhanced by the addition of
free CoA. the compound exhibited a significant inhibitory activity to the
phenylglyoxal-modified enzyme, A marked deuterium isotope effect in the cat
alytic reaction of the native synthase-NADPH complex was appreciably decrea
sed in the chemically modified enzyme. These results strongly suggest that
an electrostatic interaction between the phosphate group attached to the 2
' -position of adenosyl moiety of NADPH and the phenylglyoxal-sensitive ami
no acid residue, probably arginine, at the reaction center of 6-hydroxymell
ein synthase regulates several biochemical properties of this multifunction
al enzyme. (C) 2001 Elsevier Science BN. All rights reserved.