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Mechanism of inactivation of UDP‐glucose 4‐epimerase from Saccharomyces cerevisiac by D ‐xylose and L ‐arabinose
Author(s) -
Cármenes Ricardo S.,
Gascón Santiago,
Moreno Fernando
Publication year - 1986
Publication title -
yeast
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.923
H-Index - 102
eISSN - 1097-0061
pISSN - 0749-503X
DOI - 10.1002/yea.320020205
Subject(s) - xylose , arabinose , biology , sugar , biochemistry , galactose , ethanol , nad+ kinase , in vitro , fermentation , enzyme
In a previous paper (Cármenes et al. , 1984) we reported that UDP‐glucose 4‐epimerase from Saccharomyces was inactivated both in vitro (Crude extracts) by L ‐arabinose or D ‐xylose. In this paper, we reported that pure epimerase requires the presence of UMP or UDP to be inactivated by sugars and that the inactivation is due to the reduction of the epimerase NAD + , which is essential for epimerase activity. The inactivation rate is directly proportional to epimerase and sugar concentrations and hyperbolically proportional to UMP concentration. In situ experiments made with permeabilized cells showed that epimerase is inactivated in the same way when it is inside the cell. In vivo studies showed that epimerase is inactivated to a smaller extent when 1% D galactose is present in the culture medium than when 1% ethanol is the main carbon source.