Regulation of Aspartokinase in Azotobacter Species

Robert-Géro, Malka; Sala‐Trepat, José M.; Borgne, L. Le

doi:10.1099/00221287-67-2-189

Cited by 10 publications

(6 citation statements)

References 16 publications

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“…These two groups of Azotobacter species also diverge in other biochemical aspects since the species chroococeum, beijerinckii and vinelandii have a very closely related DNA base composition very different to that found in the species macrocytogenes and insignis (De Ley and Park, 1966), and the ability to utilize aromatic compounds as sole source of carbon and energy is widespread in the first group whereas it is almost absent in the latter (SalaTrepat, to be published). It is also noteworthy that the pattern of regulation of aspartokinase in strains of A.ehroococcum, A. vinelandii and A. beijerinckii was found to differ quantitatively from that operating in A.macrocytogenes and A.insignis strains (Robert-Gero et al, 1971). The control of homoserine dehydrogenase activity in the genus Azotobaeter appears to be somewhat different from the other bacterial dehydrogenases hitherto studied.…”

Section: Allosteric H~hibition Of Homoserine Dehydrogenase By L-threomentioning

confidence: 75%

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Regulation of homoserine dehydrogenase inAzotobacter species

Sala‐Trepat¹,

Robert-Géro²,

Borgne³

1972

Antonie van Leeuwenhoek

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SALA-TREPAT, J. M., ROBERT-GERo, M. and LE BORGNE, L. 1972. Regulation of homoserine dehydrogenase in Azotobacter species. Antonie van Leeuwenhoek: 38: 493-503.The regulation of homoserine dehydrogenase activity was studied in nine Azotobacter strains belonging to five different species. In all the species the enzyme is subject to feedback inhibition by L-threonine and L-isoleucine, the first being much more active as inhibitor. The inhibition by L-threonine is noncompetitive with respect to NADPH and of mixed type with respect to aspartate-f3-semialdehyde; the inhibition by L-isoleucine is noncompetitive with respect to both substrates. The synthesis of homoserine dehydrogenase in Azotobacter chroococcum I.P. is somewhat repressed by 1 mM L-methionine and 5 mM L-isoleucine. In all the strains examined either NADPH or NADH can serve as cofactors for this activity, though the ratio of activity with the two pyridine nucleotides (NADPH/NADH) shows higher values (3.3-3.8) in the species macrocytogenes and insignis than in the chroococcum, beijerhTckii and vinelandii group (1.5-1.6). The pattern of control of this enzyme in the genus Azotobacter is discussed in relation to other bacterial homoserine dehydrogenases.

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Section: Allosteric H~hibition Of Homoserine Dehydrogenase By L-threomentioning

confidence: 75%

“…The Azotobacter strains, buffers, growth media, and culture conditions for the normal growth and for the repression experiments, as well as the preparation of cell-free extracts have been described previously (Robert-Gero, Sala-Trepat and Le Borgne, 1971).…”

Section: Methodsmentioning

confidence: 99%

Regulation of homoserine dehydrogenase inAzotobacter species

Sala‐Trepat¹,

Robert-Géro²,

Borgne³

1972

Antonie van Leeuwenhoek

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“…The distinguishing property of type IV aspartokinase activity is the absence of an effect by L-methionine and L-isoleucine on either activity or on the inhibition by L-threonine and L-lysine. In these respects, the aspartokinases of A. communis and A. vaga resemble that of the fluorescent pseudomonads (Cohen et al, 1969) and azotobaeters (Robert-Gero et al, 1971). …”

Section: Discussionmentioning

confidence: 92%

“…This type of control of aspartokinase activity was discovered in Rhodopseudomonas capsulatus and designated "concerted feedback inhibition" by Datta and Gest (1964a). Subsequently, concerted feedback inhibition by L-threonine and L-lysine has been found in the pseudomonads (Cohen et al, 1969;Robcrt-Gero et al, 1970), the azotobacters (Robert-Gero et al, 1971), photosynthetic bacteria (Datta, 1969;Datta and Gest, 1964a,b), species of the genus Bacillus (Kuramitsu, 1970;Paulus and Gray, 1967;Rosner andPaulus, 1971, Stably andBernlohr, 1967), Micrococcus glutamicus (Nakayama et al, 1966), and Brevibacterium /lavum (Shiio and Miyajima, 1969). In addition to the concerted feedback inhibition by L-threonine and L-lysine, aspartokinase activity may be affected by other end products of the pathway.…”

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Regulation of aspartokinase activity in non-fermentative, marine eubacteria

Baumann

1974

Arch. Microbiol.

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Summary. Cell-free extracts of gram-negative, non-fermentative, marine eubacteria were assayed for aspartokinase activity. The organisms tested included polarly flagellated species and groups which had GC contents in their DNAs of 46 to 64 moles 0/o (Alteromonas, Pssudomonas) as well as species which had peritrichous flagellation and moles ~ GC contents of 53 to 68 (Alcaligenes). The results of these studies suggested that in all the strains tested, aspartokinase activity was catalyzed by a single enzyme. On the basis of the effect of L-threonine, L-lysine, L-methionine, and L-isoleucine on activity, five different types of aspartokinases (designated I through V) were delineated. In aspartokinase types I through IV, L-threonine and L-lysine inhibited activity by means of a concerted feedback inhibition; in type V, activity was inhibited by L-threonine but unaffected by L-lysine. In types I, III, and IV, L-threonine and n-lysine alone were inhibitory, while in type II these effectors had virtually no effect on activity when tested singly. Three distinct responses were observed in the presence of two other end products of the aspartate pathway, L-methionine and L-isoleucine. In types I and I[, these two amino acids usually stimulated activity and overcame the inhibition by L-threonine and n-lysine; in types IV and V, ~.-methionine and L-isoleucine had no effect; and in type III these amino acids inhibited activity. The results of this study indicate that the aspartokinases of a number of species and groups of marine bacteria have similarities and differences which should be of use in making future taxonomic groupings.The first reaction in the branched pathway leading to the biosynthesis of L-lysine, L-methionine, L-threoninc, and L-isoleucine involves the phosphorylation of aspartic acid to give fl-aspartyl phosphate. The work of Cohen and his collaborators (Cohen, 1965(Cohen, , 1968Truffa-Bachi and Cohen, 1968) has shown that in Escherichia coli K12 the control of this reaction is mediated means of three isofunctional aspartokinases (designated I, II, and III) The activities of aspartokinases I and II are feedback inhibited by L-threonine and L-lysine, respectively, while the activity of aspartokinase II is unaffected by these amino acids. This pattern of control is present in a large group of facultatively anaerobic, gram-negative bacteria of terrestrial origin which includes the peritriNon-Standard Abbreviation. GC = guanine plus cytosine.1 Arch. Microbiol., Vol. 95

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“…Feedback-insensitive mutants have been isolated from a number of bacterial species: E. coli, Bacillus subtilis, Bacillus licheniformis, Cornynebacterium glutamicum, and a methylotrophic Bacillus sp. Aspartokinase activity in A. vinelandii AMOP was measured according to the procedure of Stadtman et al (23) as modified by Robert-Gero et al (17). The wild-type strain AMOP exhibited a level of aspartokinase of about 15 U/mg of protein which was inhibited by both threonine and lysine (Fig.…”

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Selection and Characterization of Aspartokinase Feedback-Insensitive Mutants of Azotobacter vinelandii

Ekechukwu¹,

Burns²,

Melton³

1995

Appl Environ Microbiol

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Aspartokinase feedback-insensitive mutants of Azotobacter vinelandii were selected as resistant to L-threonine, ␤-hydroxynorvaline, or S-(2-aminoethyl)-L-cysteine. L-Threonine-resistant strains were classified into three groups based on their ability to transport L-threonine and their growth response to O-methylthreonine and ␤-hydroxynorvaline. Most of the mutants were transport defective; however, some were desensitized to feedback regulation.

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Regulation of Aspartokinase in Azotobacter Species

Cited by 10 publications

References 16 publications

Regulation of homoserine dehydrogenase inAzotobacter species

Regulation of homoserine dehydrogenase inAzotobacter species

Regulation of aspartokinase activity in non-fermentative, marine eubacteria

Selection and Characterization of Aspartokinase Feedback-Insensitive Mutants of Azotobacter vinelandii

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