INVESTIGADORES
RAYA Raul Ricardo
artículos
Título:
Nutritional requirements and nitrogen-dependent regulation of proteinase activity of Lactobacillus helveticus CRL 1062.
Autor/es:
HEBERT EM, RAYA RR, DE GIORI GS.
Revista:
APPLIED AND ENVIRONMENTAL MICROBIOLOGY
Editorial:
AMER SOC MICROBIOLOGY
Referencias:
Lugar: Washington; Año: 2000 vol. 66 p. 5316 - 5321
ISSN:
0099-2240
Resumen:
The nutritional requirements of Lactobacillus helveticus CRL 1062 were
determined with a simplified chemically defined medium (SCDM) and
compared with those of L. helveticus CRL 974 (ATCC 15009). Both strains
were found to be prototrophic for alanine, glycine, asparagine,
glutamine, and cysteine. In addition, CRL 1062 also showed prototrophy
for lysine and serine. The microorganisms also required riboflavin,
calcium pantothenate, pyridoxal, nicotinic acid, and uracil for growth
in liquid SCDM. The growth rate and the synthesis of their cell
membrane-bound serine proteinases, but not of their intracellular
leucyl-aminopeptidases, were influenced by the peptide content of the
medium. The highest proteinase levels were found during cell growth in
basal SCDM, while the synthesis of this enzyme was inhibited in SCDM
supplemented with Casitone, Casamino Acids, or beta-casein.
Low-molecular-mass peptides (<3,000 Da), extracted from Casitone, and
the dipeptide leucylproline (final concentration, 5 mM) play important
roles in the medium-dependent regulation of proteinase activity. The
addition of the dipeptide leucylproline (5 mM) to SCDM reduced
proteinase activity by 25%.