Tsuyoshi Nakamatsu

Glutamate Overproduction in Corynebacterium glutamicum Triggered by a Decrease in the Level of a Complex Comprising DtsR and a Biotin-containing Subunit

Glutamate overproduction in Corynebacterium glutamicum is induced by Tween 40, biotin-limitation, or sublethal amounts of penicillin. Disruption of the dtsR gene, which encodes a putative component of a biotin-containing enzyme complex involved in fatty acid synthesis, causes constitutive overproduction of glutamate. We report here that overexpression of dtsR inhibits the induction of glutamate overproduction. In contrast, the level of DtsR in the wild type strain was found to decrease in the presence of Tween 40 or limited amounts of biotin. Tween 40, biotin-limitation, or dtsR disruption also reduced the activity of 2-oxoglutarate dehydrogenase complex (ODHC), which is involved in the synthesis of succinate from 2-oxoglutarate. These results indicate that decrease in the level of DtsR or a complex containing DtsR triggers the increased synthesis of glutamate from 2-oxoglutarate by lowering the ODHC activity.

Biosynthesis of lactacystin. Origin of the carbons and stereospecific NMR assignment of the two diastereotopic methyl groups

Abstract Biosynthetic pathway of lactacystin and its stereochemical aspect were investigated by feeding experiments of 13 C enriched compounds.

Microbial Production of 3-Oxobisnorchola-l,4-dien-22-oic Acid

Among examined microorganisms which have ability to decompose cholesterol, Nocardia corallim IFO 3338 converted cholesterol to 3-oxobisnorchoIa-l,4-dien-22-oic acid (BDA) at the conversion rate of 63%. The conversion product was identified as BDA by 1H-NMR, 13C-NMR, UV, IR, MS and elemental analysis.The presence of chelating agents or some metal ions was necessary for the accumulation of BDA. The most effective agents for the accumulation were α,α′-dipyridyl and o-phenanthroline.For the production of BDA, cholestanol, β-sitosterol, soy sterol (mixture), cholest-4-en-3-one and lithocholic acid could also be used as substrates other than cholesterol.

>Studies of L-Glutamate-Production in Coryneform Bacteria by Using Metabolic-Flux Analysis

Abstract An odhA-disrupted mutant extremely produce glutamate into the medium in the presence of excess amounts of biotin. This result means the mechanism of glutamate production in coryneform bacteria is irreverent to the permeability of a cell membrane. Furthermore, a noble gene, dtsR, was cloned as a multi-copy suppresser gene of a detergent sensitive mutant derived from a wildtype strain of coryneform bacteria. DtsR showed significant homologies to some biotin enzymes. A dtsR-disrupted mutant produce glutamte. The mechanism of glutamate production in coryneform bacteria was discussed.