Arfin S M, Miner T, Hatfield G W
J Bacteriol. 1974 Nov;120(2):604-7. doi: 10.1128/jb.120.2.604-607.1974.
The differential rates of synthesis of the three branched-chain aminoacyl-transfer ribonucleic acid synthetases were measured in Salmonella typhimurium LT-2 and a mutant, ilvA504. The mutant produced an l-threonine deaminase with a decreased affinity for its cofactor, pyridoxal-5'-monophosphate. The addition of pyridoxal-5'-monophosphate to cultures of strain ilvA504 growing in excess isoleucine, valine, and leucine resulted in an increased rate of growth and repression of the synthesis of the isoleucine and valine biosynthetic enzymes. No differences in the rate of synthesis of the branched-chain aminoacyl-transfer ribonucleic acid synthetases were observed in cultures of ilvA504 growing with or without added pyridoxal-5'-monophosphate. The differential rates of synthesis of all three enzymes were similar to the rates measured in strain LT-2. These experiments suggest that different forms of the ilvA gene product are involved in the regulation of the branched-chain amino acid biosynthetic enzymes and the branched-chain aminoacyl-transfer ribonucleic acid synthetases.
在鼠伤寒沙门氏菌LT-2及其突变体ilvA504中，测定了三种支链氨基酸酰基转移核糖核酸合成酶的合成差异速率。该突变体产生的L-苏氨酸脱氨酶对其辅因子磷酸吡哆醛-5'-单磷酸的亲和力降低。向在过量异亮氨酸、缬氨酸和亮氨酸中生长的ilvA504菌株培养物中添加磷酸吡哆醛-5'-单磷酸，导致生长速率增加，并抑制异亮氨酸和缬氨酸生物合成酶的合成。在添加或不添加磷酸吡哆醛-5'-单磷酸的情况下生长的ilvA504培养物中，未观察到支链氨基酸酰基转移核糖核酸合成酶合成速率的差异。所有三种酶的合成差异速率与在LT-2菌株中测得的速率相似。这些实验表明，ilvA基因产物的不同形式参与了支链氨基酸生物合成酶和支链氨基酸酰基转移核糖核酸合成酶的调控。
