TY - JOUR
T1 - Lactococcus lactis LM0230 contains a single aminotransferase involved in aspartate biosynthesis, which is essential for growth in milk
AU - Dudley, E. G.
AU - Steele, J. L.
PY - 2001
Y1 - 2001
N2 - Amino acid aminotransferases (ATases), which catalyse the last biosynthetic step of many amino acids, may have important physiological functions in Lactococcus lactis during growth in milk. In this study, the aspartate ATase gene (aspC) from L. lactis LM0230 was cloned by complementation into Escherichia coli DL39. One chromosomal fragment putatively encoding aspC was partially sequenced. A 1179 bp ORF was identified which could encode for a 393 aa, 43·2 kDa protein. The deduced amino acid sequence had high identity to other AspC sequences in GenBank and is a member of the lγ family of ATases. Substrate-specificity studies suggested that the lactococcal AspC has ATase activity only with aspartic acid (Asp). An internal deletion was introduced into the L. lactis chromosomal copy of aspC by homologous recombination. The wild-type and mutant strain grew similarly in defined media containing all 20 amino acids and did not grow in minimal media unless supplemented with asparagine (Asn). The mutant strain was also unable to grow in or significantly acidify milk unless supplemented with Asp or Asn. These results suggest that only one lactococcal ATase is involved in the conversion of oxaloacetate to Asp, and Asp biosynthesis is required for the growth of L. lactis LM0230 in milk.
AB - Amino acid aminotransferases (ATases), which catalyse the last biosynthetic step of many amino acids, may have important physiological functions in Lactococcus lactis during growth in milk. In this study, the aspartate ATase gene (aspC) from L. lactis LM0230 was cloned by complementation into Escherichia coli DL39. One chromosomal fragment putatively encoding aspC was partially sequenced. A 1179 bp ORF was identified which could encode for a 393 aa, 43·2 kDa protein. The deduced amino acid sequence had high identity to other AspC sequences in GenBank and is a member of the lγ family of ATases. Substrate-specificity studies suggested that the lactococcal AspC has ATase activity only with aspartic acid (Asp). An internal deletion was introduced into the L. lactis chromosomal copy of aspC by homologous recombination. The wild-type and mutant strain grew similarly in defined media containing all 20 amino acids and did not grow in minimal media unless supplemented with asparagine (Asn). The mutant strain was also unable to grow in or significantly acidify milk unless supplemented with Asp or Asn. These results suggest that only one lactococcal ATase is involved in the conversion of oxaloacetate to Asp, and Asp biosynthesis is required for the growth of L. lactis LM0230 in milk.
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U2 - 10.1099/00221287-147-1-215
DO - 10.1099/00221287-147-1-215
M3 - Article
C2 - 11160815
AN - SCOPUS:0035156548
VL - 147
SP - 215
EP - 224
JO - Journal of General Microbiology
JF - Journal of General Microbiology
SN - 1350-0872
IS - 1
ER -