GThreonine dehydratase catalyzes the nonoxidative conversion of /Y-substituted amino acids to cr-keto acids. In this manuscript the nature of the nucleophiles which are eliminated is established, new substrates are reported, and inhibition by j&substituted alanines investigated. It is now shown that threonine dehydratase will catalyze the q/3 elimination of -OH, -Cl, and -F as HzO, and HX from ...

Mice were injected with either SnCl2 (intraperitoneal) or Na2SeO3 (subcutaneous) alone or together at doses of 50 mumol/kg body weight. After 20 hours blood was collected and the concentrations of tin (Sn) and Selenium (Se) and the activity of 5-aminolaevulinate hydrolyase (ALA dehydratase, EC 4.2.1.24) in blood were determined. The concentrations of Sn in whole blood were 4.9 (SD 1.5) nmol/ml ...

We report on the identification of Mycobacterium tuberculosis HtdZ (Rv0130), representing a novel 3-hydroxyacyl-thioester dehydratase. HtdZ was picked up by the functional complementation of Saccharomyces cerevisiae htd2Delta cells lacking the dehydratase of mitochondrial type II fatty acid synthase. Mutant cells expressing HtdZ contained dehydratase activity, recovered their respiratory abilit...

Pretyrosine, an intermediate of L-tyrosine biosynthesis in blue-green algae, was found to be enzymatically formed and utilized in Pseudomonas aeruginosa. The enzymology and regulation of aromatic biosynthesis were re-evaluated in the context of these new findings, Four species of aromatic aminotranaferase were separated and partially purified. Each was reactive with prephenate, phenylpyruvate, ...

The activity of S-aminolevulinic acid (ALA) dehydratase. an enzyme involved in heme biosynthesis. has been shown to increase in Friend virus-transformed murine erythroleukemia (MEL) cells during erythroid differentiation. In this study. the nature of the increase in ALA dehydratase activity in MEL cells was examined using a monospecific antibody directed to the enzyme. A sevenfold increase in A...

The gene encoding threonine synthetase has been located by genetic transformation in Bacillus subtilis. Its position is adjacent and central to the genes encoding homoserine dehydrogenase and homoserine kinase. Its mutational sites are closely linked to, and interspersed among, several mutational sites affecting a minor but phenotypically significant threonine dehydratase (distinct from the maj...

Kinetic and aggregatory properties of a partially purified preparation of D-erythro-imidazoleglycerol phosphate dehydratase-histidinol phosphate phosphatase from a derepressed mutant of Salmonella typhimurium (his012$2) have been investigated. The molecular weight in crude extracts is 300,000. Purification of the enzyme causes disaggregation, the main component keing 75,000 in molecular weight....

Glycerol and diol dehydratases are inducible, coenzyme B12-dependent enzymes found together in Klebsiella pneumoniae ATCC 25955 during anaerobic growth on glycerol. Mutants of this strain isolated by a novel procedure were separately constitutive for either dehydratase, showing the structural genes for the two enzymes to be under independent control in vivo. Glycerol dehydratase and a trimethyl...

An elaborate and apparently unique specialization of the endoplasmic reticulum having the form of tubules and a precise orientation with respect to the mitochondria has been described for the specific cell of the pseudobranch gland. The tubules also are concentrated near the vascular border of the cell where they show continuity with the plasma membrane and open directly against the basement me...

Evidence is provided that dromedary heavy-chain antibodies, in vivo-matured in the absence of light chains, are a unique source of inhibitory antibodies. After immunization of a dromedary with bovine erythrocyte carbonic anhydrase and porcine pancreatic alpha-amylase, it was demonstrated that a considerable amount of heavy-chain antibodies, acting as true competitive inhibitors, circulate in th...