l-Homoserine Fermentation

Abstract

.In the course of studies on "negative feedback control" rnechanisnls caused by threonine and nlethionine in L-homoserine fermentation with Micrococcus glutarnicus 534:-Co147 culture, L-homoserine dehydrogenase was first found to occur in the culture, and effects of various amino acids on the formation and action of the enzyme wcre then invcstigated. The rcsult was that L-homoserine dehydrogenase of the culture was repressed by methionine on the one hand, and inhibited by threonine on the other. .a-Aspartokinase was found not to be reprcsscd by methionine. From these findings, the sites at which the "negative feedback control" mechanisms work were discussed.

Studies on the biosynthesis of porphyrin and bacteriochlorophyll by Rhodopseudomonas spheroides. 3. The effect of threonine on the biosynthesis of homoserine and methionine

“…Like aspartate fisemialdehyde dehydrogenase the homoserine dehydrogenase of Rp8. spheroides is specific for NADP+ and does not utilize NAD+; it is sinmilar in this respect to the homoserine dehydrogenase in M. glutamicus (Nara et al 1961), but different from the one in baker's yeast (Black & Wright, 1955c), which can use both nucleotides. The rate of reduction was linear for 5 min.…”

“…spheroide8 the homoserine dehydrogenase can utilize only NADP, whereas the corresponding enzyme from yeast utilizes both NADP and NAD and in fact has a greater affinity for the latter. Nara et al (1961) found that the homoserine dehydrogenase from M. glutamicus also was specific for NADP. The work reported here is consistent with the postulate that threonine inhibits the production of bacteriochlorophyll in Rp8.…”

“…In S. cerevi8iae, where lysine is synthesized by another pathway not involving aspartic acid, there is only one f-aspartokinase which is both inhibited and repressed by threonine. However, in Micrococcus glutamicus, homoserine dehydrogenase, the enzyme catalysing the conversion of aspartate ,B-semialdehyde into homoserine, is strongly inhibited by threonine, and its synthesis is repressed by growth in the presence of methionine (Nara et al 1961). In Rp8.…”

Na+-Dependent Transport of Amino Acids and Its Significance for Growth of a Lysine-producing Bacterium

“…(1 ) lysine-producing ability of HUT 8052, it is suggested that the mutant is a threonine plus methionine (or homoserine) auxotroph which is genetically blocked at least at 2 steps; the first step is conversion of homoserine to threonine, and the second step is homo serine dehydrogenase in the biosynthetic pathwayI6) of the amino acids of aspartic acid family (Fig, 3), Measurement of homo serine dehydrogenase activity in HUT 8052 revealed its drastic reduction in comparison with that in the wild strain (Table I) * ASA, Aspartate-/i'-semialdehyde, ** Hom" Homoserine, above, the mutant grew slightly in the absence of methionine (or homoserine) under a certain condition, Thus the block at homo serine dehydrogenase seems to be incomplete, The homoserine dehydrogenase in "glutamic acidproducing bacteria" is apt to get feedback inhibition by threonine, 15,16) Consequently, the addition of a large amount of threonine in a growth medium reduces the growth of the bacterium by inhibiting the homoserine dehydrogenase and then inhibiting the synthesis of methionine. The reduction of homoserine dehydrogenase activity would lead the strain to be more sensitive to threonine.…”

l-Methionine Production by Methionine Analog-resistant Mutants OfCorynebacterium glutamicum

“…154 H. KASE and K. NAKAYAMA L-Methionine has been produced by resolution of racemic DL-methionine or by hydrolysis of protein. As for microbial process, the conversion of DL-2-hydroxy-4-methylthiobutyric acid 21 or DL-5-(p-methylmercaptoethyl)-hydantoin 31 into L-methionine by various microorganisms has been reported. However, there is a dearth of report on fermentation production of L-methionine.…”