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GrainGenes Reference Report: BCJ-313-669

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Reference
BCJ-313-669
Title
Effects of lipids on nucleotide inhibition of wheat-germ aspartate transcarbamoylase: evidence of an additional level of control
Journal
Biochemical Journal
Year
1996
Volume
313
Pages
669-673
Author
Khan A
Chowdhry B
Yon R
Abstract
Wheat-germ aspartate transcarbamoylase, a monofunctional trimer, is strongly inhibited by uridine 5'-monophosphate (UMP), which shows kinetic interactions with the substrate, carbamoyl phosphate, suggesting a classical allosteric mechanism of regulation Inhibition of the purified enzyme by UMP was amplified in the presence of a variety of ionic lipids at concentrations low enough to preclude denaturation In the absence of UMP, most of these compounds had no kinetic effect or were slightly activating Two phospholipids did not show the effect In a homologous series of fatty acids (C6-C16), the potentiating effect was only seen with homologues greater than C8, reaching a maximum at C12 The effect of dodecanoate (C12) on kinetic cooperativity (UMP as variable ligand) was studied At each of several fixed concentrations of carbamoyl phosphate, dodecanoate had a pronounced effect on the half-saturating concentration of UMP, which was reduced by about half in every case. indicating substantially tighter binding of UMP. However, dodecanoate had relatively little effect on the kinetic Hill coefficient for the cooperativity of UMP. The possible metabolic significance of these effects is discussed.
Keyword
[ Hide all but 1 of 11 ]
carbamoyl-phosphate
enzyme activity
fatty-acids
inhibition
phosphates
regulation
sulfonates
transferases
triticum aestivum
ump
wheat germ

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