Characterization of the L-lysine biosynthetic pathway in the obligate methylotroph Methylophilus methylotrophus.
The L-lysine biosynthetic pathway of the gram-negative obligate methylotroph Methylophilus methylotrophus AS1 was examined through characterization of the enzymes aspartokinase (AK), aspartsemialdehyde dehydrogenase, dihydrodipicolinate synthase (DDPS), dihydrodipicolinate reductase, and diaminopimelate decarboxylase. The AK was inhibited by L-threonine and by a combination of L-threonine and L-lysine, but not by L-lysine alone, and the activity of DDPS was moderately reduced by L-lysine. In an L-lysine producing mutant (G49), isolated as an S-(2-aminoethyl)-L-cysteine (lysine analog) resistant strain, both AK and DDPS were partially resistant to feedback inhibition. The ask and dapA genes encoding AK and DDPS respectively were isolated from the parental strain, AS1, and its G49 derivative. Comparison of the sequences revealed a point mutation in each of these genes in G49. The mutation in the ask gene altered aspartic acid in a key region involved in the allosteric regulation common to AKs, while a novel mutation in the dapA gene altered tyrosine-106, which was assumed to be involved in the binding of L-lysine to DDPS.
Gunji
Yoshiya
Y
Fermentation and Biotechnology Laboratories, Ajinomoto Co., Inc, 1-1 Suzuki-cho, Kawasaki-ku, Kawasaki 210-8681, Japan.
Tsujimoto
Nobuharu
N
Shimaoka
Megumi
M
Ogawa-Miyata
Yuri
Y
Sugimoto
Shin-Ichi
S
Yasueda
Hisashi
H
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D001222:Aspartate Kinase / Q000235:genetics / Q000378:metabolism; D001223:Aspartate-Semialdehyde Dehydrogenase / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002262:Carboxy-Lyases / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D050746:Dihydrodipicolinate Reductase; D005246:Feedback; D006836:Hydro-Lyases / Q000235:genetics / Q000378:metabolism; D008239:Lysine / Q000096:biosynthesis*; D020630:Methylophilus methylotrophus / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
D000596:Amino Acids; D004269:DNA, Bacterial; D011994:Recombinant Proteins; D050746:Dihydrodipicolinate Reductase; D001223:Aspartate-Semialdehyde Dehydrogenase; D044925:Oxidoreductases Acting on CH-CH Group Donors; D001222:Aspartate Kinase; D002262:Carboxy-Lyases; D006836:Hydro-Lyases; C020040:4-hydroxy-tetrahydrodipicolinate synthase; D008239:Lysine