The gene encoding the glutamate dehydrogenase in Lactococcus lactis is part of a remnant Tn3 transposon carried by a large plasmid.

The gene responsible for the uncommon glutamate dehydrogenase (GDH) activity of Lactococcus lactis was identified and characterized. It encodes a GDH of family I that is mainly active in glutamate biosynthesis, is carried by a large plasmid, and is included, with functional cadmium resistance genes, in a remnant Tn3-like transposon.

Selection and properties of Streptococcus thermophilus mutants deficient in urease.

Natural variations of the urea content of milk have a detrimental effect on the regularity of acidification by Streptococcus thermophilus strains used in dairy processes. The aim of the present study was to select urease-deficient mutants of S. thermophilus and to investigate their properties.

Effect of the metabolism of urea on the acidifying activity of Streptococcus thermophilus.

One of the main functions of Streptococcus thermophilus strains used in the dairy industry is the production of lactic acid. In cheese and fermented milk manufacturing processes, the pH evolution kinetics must be reproducible in order to ensure the good quality of the final products. The objective of the present study was to investigate the effect of the metabolism of urea on the acidifying activity of fast- and slow-acidifying strains of S.

Itaconate biosynthesis in Aspergillus terreus.

Itaconate biosynthesis was studied in intact cells of high-yield (RC4') and low-yield (CM85J) strains of the fungus Aspergillus terreus by methods (tracers, nuclear magnetic resonance spectroscopy, and mass spectroscopy) that did not interfere with metabolism. Itaconate formation in RC4' required de novo protein biosynthesis. Krebs cycle intermediates increased in both strains during the production of itaconic acid.

Role of the 1-amino group in aminocyclitol antibiotics: synthesis of 1-deaminogentamicin C2.

The synthesis of 1-deaminogentamicin C2 described here, uses 3,2',6',3"-tetrakis-N-tert-butoxycarbonylgentamicin C2 (2) as intermediate. N-Formylation of 2 followed by per-O-acetylation and dehydration furnished the isocyanide 5. Radical-induced deamination of the latter using tri-n-butylstannane and removal of the protecting groups afforded the target 1-deaminogentamicin C2 (7).

1-N-acylation of gentamicin C1a by a cyclic, chiral gamma-amino-alpha-hydroxy acid related to the (S)-4-amino-2-hydroxybutyric acid.

A semisynthetic aminoglycoside antibiotic 15, containing a cyclic gamma-amino-alpha-hydroxy acid, related to the 1-N-4-amino-2-hydroxybutyric acid (AHBA) side chain of butirosins and amikacin, has been prepared. Conveniently protected 3,2',6'-tris-N-tert-butoxycarbonylgentamicin C1a (12) was condensed with the phtalimido active ester 10 to give after catalytic reduction and deprotection, the hitherto unknown 1-N-substituted gentamicin C1a 15. The requisite side chain was synthesized from the readily available D-(-)-quinic acid.

Sub-unit assembly in the biosynthesis of neomycin. The synthesis of 5-O-beta-D-ribofuranosyl and 4-O-beta-D-ribofuranosyl-2,6-dideoxystreptamines.

The preparation of the deoxy- analogues of two pseudodisaccharide fragments of neomycin, 5-O-beta-D-ribofuranosyl-2,6-dideoxy-streptamine and 6-deoxyneamine is described. When added to the growth medium of a deoxystreptamine-idiotroph of Streptomyces rimosus forma paromomycinus only the latter was incorporated into antibiotic, suggesting an obligatory order for the assembly of sub-units. 4-O-beta-D-Ribofuranosyl-2,6-dideoxystreptamine was also prepared.