Evidence published in recent years has shown that the biosynthesis of valine and isoleucine proceeds by a similar sequence of reactions (24). Fig. 1 depicts the reactions considered to be involved. In this report only Reactions II, III, and IV will be considered. Reaction II, the isomerization of the Lu-hydroxy$keto acid (ac-acetolactate for valine biosynthesis and a-aceto-a-hydroxybutyrate for...

Growth assays and nitrogen balance trials were conducted in an attempt to estimate requirements for threonine, isoleucine, valine and leucine. Weanling kittens were fed a basal purified diet containing 27% crystalline L-amino acids and 4,700 kcal metabolizable energy per kilogram diet. Based upon rate and efficiency of growth, and upon urinary nitrogen excretion, estimated requirements for thre...

A group of mutants of Neurospora crassa which require both isoleucine and valine have been described in a series of previous communications from this laboratory (WAGNER, SOMERS and BERGQUIST 1960; WAGNER, KIRITANI and BERGQUIST 1962; and KIRITANI 1962). These mutants were all found to be closely linked between the linkage group V markers Zys-1 (lysine-1, 33933) and sp (spray) within a segment a...

Several streptomycin-resistant mutants of Escherichia coli have been isolated which require exogenous isoleucine for growth. The majority of these strains were of streptomycin-dependent phenotype. If grown in the absence of streptomycin, these streptomycin-dependent auxotrophs (Sm(d-aux)) strains were unable to produce beta-galactosidase and aldolase activities and also failed to exhibit donor ...

Two threonine dehydratases, I and 11, were found to occur in Euglena gracilis and each enzyme was purified partially. Like the biosynthetic threonine dehydratases of other organisms, dehydratase I was feedback-inhibited by isoleucine and not affected by adenylates. Dehydratase I1 was not influenced by branched-chain amino acids and adenylates. Occurrence of dehydratase 11, with a much higher ac...

Analogues of deamino-ti-carba-oxytocin, containing isoleucine, Ocmethyltyrosine or methionine in position 2, either in the sulfide or sulfoxide form, were prepared and studied pharmacologically. These compounds had considerably lower biological activities than the analogous compounds of the l-carba series. Furthermore, analogues of [l,6-homolanthionine]deamino-oxytocin were prepared with Ocmeth...

Biochemical and genetic analyses of the bacterium Salmonella typhimurium suggest that accumulation of alpha-ketobutyrate partially mediates the herbicidal activity of acetolactate synthase inhibitors. Growth inhibition of wild-type bacteria by the herbicide sulfometuron methyl was prevented by supplementing the medium with isoleucine, an allosteric inhibitor of threonine deaminase-catalyzed syn...