A NADP-glutamate dehydrogenase mutant of the petit-negative yeast Kluyveromyces lactis uses the glutamine synthetase-glutamate synthase pathway for glutamate biosynthesis.
The activities of the enzymes involved in ammonium assimilation and glutamate biosynthesis were determined in wild-type and NADP-glutamate dehydrogenase (GDH) null mutant strains of Kluyveromyces lactis. The specific NADP-GDH activity from K. lactis was fivefold lower than that found in Saccharomyces cerevisiae. The glutamine synthetase (GS) and glutamate synthase (GOGAT) activities were similar to those reported in S. cerevisiae. The NADP-GDH null mutant was obtained by transforming the uraA strain MD2/1 with a linearized integrative yeast vector harbouring a 390 bp fragment of the NADP-GDH structural gene. This mutant grew as well as the parent strain on ammonium, but showed GS and GOGAT activities higher that those found in the wild-type strain, implying that the GS-GOGAT pathway could play a leading role in glutamate biosynthesis in K. lactis. Southern blotting analysis of K. lactis chromosomes separated by contour-clamped homogeneous electric field electrophoresis, indicated that the NADP-GDH structural gene is localized on chromosome VI.
Valenzuela
L
L
Departamento de Microbiología, Universidad Nacional Autónoma de México, Mexico City, Mexico.
Guzmán-León
S
S
Coria
R
R
Ramírez
J
J
Aranda
C
C
González
A
A
D000595:Amino Acid Sequence; D001483:Base Sequence; D002874:Chromosome Mapping; D005798:Genes, Bacterial; D005969:Glutamate Dehydrogenase / Q000235:genetics*; D005970:Glutamate Synthase / Q000378:metabolism*; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism*; D018698:Glutamic Acid / Q000096:biosynthesis*; D007716:Kluyveromyces / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation
D018698:Glutamic Acid; D005970:Glutamate Synthase; D005969:Glutamate Dehydrogenase; D005974:Glutamate-Ammonia Ligase