Regulation of aspartokinase, aspartate semialdehyde dehydrogenase, dihydrodipicolinate synthase and dihydrodipicolinate reductase in Lactobacillus plantarum.
The use of a lysine-overproducing strain of Lactobacillus plantarum in food or feed fermentations may lead to the production of lysine-rich products. The availability of functional genes and information on the regulation of lysine biosynthesis are required to develop a lysine-overproducing strain. The genome sequence of L. plantarum revealed putative lysine biosynthetic genes, some of which may produce isozymes. This study examined the functionality of the genes and the regulation of the first four enzymes of lysine biosynthesis, together with homoserine dehydrogenase, in L. plantarum. The genes were expressed in Escherichia coli, and the regulation of the enzymes was studied in cell extracts of both recombinant E. coli and L. plantarum. Among seven lysine biosynthetic genes studied (aspartokinase genes, thrA1 and thrA2; aspartate semialdehyde dehydrogenase genes, asd1 and asd2; dihydrodipicolinate synthase genes, dapA1 and dapA2; and the dihydrodipicolinate reductase gene, dapB) plus two homoserine dehydrogenase genes (hom1 and hom2), the products of six genes, i.e. thrA2, asd2, dapA1, dapB, hom1 and hom2, showed obvious enzyme activities in vitro. The product of one of the homoserine dehydrogenase genes, hom1, exhibited both homoserine dehydrogenase and aspartokinase activities. However, the aspartokinase activity was mainly due to ThrA2 and was inhibited by L-lysine and repressed by L-threonine, and the homoserine dehydrogenase activity was mainly due to Hom2 and was inhibited by L-threonine. The aspartate semialdehyde dehydrogenase, dihydrodipicolinate synthase and dihydrodipicolinate reductase were not regulated by the end-products of the pathway.
Cahyanto
Muhammad N
MN
The International Center for Biotechnology, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
Kawasaki
Hiroko
H
The International Center for Biotechnology, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
Nagashio
Mariko
M
The International Center for Biotechnology, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
Fujiyama
Kazuhito
K
The International Center for Biotechnology, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
Seki
Tatsuji
T
The International Center for Biotechnology, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
D001222:Aspartate Kinase / Q000235:genetics / Q000378:metabolism*; D001223:Aspartate-Semialdehyde Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D050746:Dihydrodipicolinate Reductase / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D016680:Genome, Bacterial; D006715:Homoserine Dehydrogenase / Q000235:genetics; D006836:Hydro-Lyases / Q000235:genetics / Q000378:metabolism*; D048191:Lactiplantibacillus plantarum / Q000235:genetics / Q000378:metabolism*; D008239:Lysine / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013912:Threonine / Q000494:pharmacology
D011994:Recombinant Proteins; D013912:Threonine; D006715:Homoserine Dehydrogenase; D050746:Dihydrodipicolinate Reductase; D001223:Aspartate-Semialdehyde Dehydrogenase; D001222:Aspartate Kinase; D006836:Hydro-Lyases; C020040:4-hydroxy-tetrahydrodipicolinate synthase; D008239:Lysine