Repression of Escherichia coli pyridine nucleotide transhydrogenase by leucine

Abstract

Reteive,d forpublication 26 October. 1977 Addition of 0.1% casein hydrolysate to a iniiiimal growth medium decreased membrane-bound transhydrogenase activity in Escherichia coli by about 80%. Of the amino acids added individually to the growth medium, only leucine and, toa lesser extent, methionine and alanine were effective. a-Ketoisocaproateand leucine-containing'peptides repressed the activity, and leucine also repressed activity in adenyl cyclase-deficient and relaxed strains. Derepression of transhy

The respiratory chains of Escherichia coli.

“…The enzyme is coinduced with NAD(P)+ glutamate dehydrogenase under conditions of nitrogen limitation and when ammonium iops are the sole nitrogen source; it has been suggested that the transhydrogenase is the source of NADPH for ammonia assimilation (300). Transhydrogenase activity is suppressed by leucine and, to a lesser extent, by methionine and alanine (153). NADPH formation during growth on glucose has been studied in wild-type and mutant strains affected in NADPHgenerating reactions (glucose-6-phosphate dehyd,rogenase, isocitrate dehydrogenase, malate dehydrogenate, and energy-linked transhydrogenase [96]).…”

Microbial energetics

“…It appears that this enzyme is required for NADPH synthesis and, for thermodynamic reasons, cannot be energy-conserving (Jones 1977). Its synthesis is repressed by amino acids, particularly leucine (Gerolimatos & Hanson 1978), and mutants with defects in their ability to produce the enzyme have been described (Zahl et at. 1978).…”

Coregulation of oxidized nicotinamide adenine dinucleotide (phosphate) transhydrogenase and glutamate dehydrogenase activities in enteric bacteria during nitrogen limitation

“…The involvement in NADPH production for general biosynthesis is, however, not borne out by recent studies designed to probe cellular sources of NADPH (4). A role for the enzyme in branched-chain amino acid transport has also been suggested (5). Evidence was presented that leucyl-tRNA functions as a regulator of the enzyme.…”