Regulation of homoserine dehydrogenase inAzotobacter species

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

doi:10.1007/bf02328116

Cited by 1 publication

(4 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The relationship between the induction of ortho and meta pathways therefore appears to be the same as in Pseudomonus putidu NCIB 10015, where phenol and the cresols being inducers "from the top" of the meta pathway enzymes are assimilated by this pathway, but substrates which are converted to catechol and which are not inducers of the meta pathway, as benzoate in the case of Pseudomonas putida NCIB 10015, are assimilated by the ortho pathway [ZZ]. These experiments confirm the observations in other organisms [8,22,23] that the metabolic function of the meta pathway is the nonspecific assimilation of catechol and methylcatechols and their precursors, whereas the ortho pathways appear capable of only metabolising catechol and its precursors.…”

Section: Discussionsupporting

confidence: 70%

“…Some of the scheme however has not been verified directly. As in our experiments with Pseudomonas putida NCIB 10015 [8] we have not demonstrated the participation of 2-oxopent-4-enoate or its methyl analogue, nor have we been able to assay for 2-0x0pent-4-enoate hydratase. However, in other organisms using the meta pathway 2-oxopent-4-enoate has been shown to be the product of both2-hydroxymuconic semialdehyde hydrolase [3,6] and of 4-oxalocrotonate decarboxylase [3], and 2-oxopent-4-enoate hydratase has been purified to homogeneity [19].…”

Section: Discussionmentioning

confidence: 61%

“…Since benzoate appears to be an inducer it is not unreasonable to propose that in m-and p-toluategrown cells the induction of this same set of enzymes is also by the growth substrate. As with Pseudomonas putida NCIB 10015 [8,22] and Pseudomonm aeruginosa T1 [14], the meta pathway enzymes are both nonspecific in their action and also nonspecifically induced, thus giving the cell a considerable range of metabolic potential with a limited amount of genetic material.…”

Section: Discussionmentioning

confidence: 99%

“…The procedures for assaying and definition of the units of activity of catechol2,3-oxygenase, 2-hydroxymuconic semialdehyde hydrolase, 2-hydroxymuconic semialdehyde dehydrogenase, 4-oxalocrotonate tautomerase and 4-hydroxy-2-oxovalerate aldolase were as previously described [3,8].…”

Section: Enzyme Assaysmentioning

confidence: 99%

See 3 more Smart Citations

The Metabolism of Benzoate and Methylbenzoates via the meta‐Cleavage Pathway by Pseudomonas arvilla mt‐2

Murray

Duggleby

Williams

et al. 1972

European Journal of Biochemistry

137

View full text Add to dashboard Cite

1. Pseudomonas arvilla mt-2 grows a t the expense of benzoate, m-toluate (3-methylbenzoate) and p-toluate (4-methylbenzoate), but not o-toluate (2-methylbenzoate). Under various conditions compounds with spectra characteristic of muconic semialdehydes can be made to accumulate in the media. These spectra indicate that benzoate is metabolised through catechol and 2-hydroxymuconic semialdehyde (2-hydroxy-6-oxohexa-2,4-dienoate), m-toluate through 3-methylcatechol and 2-hydroxy-6-oxohepta-2,4-dienoate and p-toluate through 4-methylcatechol and 2-hydroxy-5-methylmuconic semialdehyde (2-hydroxy-5-methyl-6-oxohexa-2,4-dienoate).2. Freshly harvested cells grown on all three substrates only consume oxygen a t a significant rate when presented with the growth substrates themselves and catechol and the methylcatechols, but not with salicylate, protocatechuate or phenol or the cresols.3. Extracts of cells grown on these substrates contain high induced levels of the suite of meta cleavage enzymes, including both the hydrolytic branch and the 4-oxalocrotonate branch.4. The substrate specificity of the early enzymes of the pathway suggests that only one nonspecific enzyme expresses each activity in cell-free extracts and that it is nonspecifically induced during growth on all three carbon sources. 5.It is suggested that the metabolic role of the hydrolytic branch of the pathway is the assimilation of 3-methylcatechol and its precursor, and that of the 4-oxalocrotonate branch is to assimilate catechol and 4-methylcatechol and their precursors.6. o-Toluate is not metabolised because it is neither a substrate for the benzoate oxidase system nor an inducer of any of the meta pathway enzymes.7 . It appears that benzoate and m-and p-toluates are the substrate inducers of the meta pathway enzymes in this organism. The ortho pathway is induced on incubating cells with catechol and the first inducer appears to be &,cis-muconate or possibly catechol itself.The coexistence of two enzymes able to degrade the meta cleavage product of catechol, 2-hydroxymuconic semialdehyde, was first demonstrated in cell-free extracts of both benzoate-grown Azotobacter species [l] and a naphthalene-grown Pseudomonas strain NCIB 9816 [2]. Sala-Trepat and Evans [3] elucidated the two resulting pathways, which after diverging a t 2-hydroxymuconic semialdehyde converge again a t 2-oxopent-4-enoate ; they concluded that in Azotobacter only the 4-oxalocrotonate branch, involving as the first step the NADf-dependent dehydrogenation of 2-hydroxymuconic semialdehyde, was of any metabolic significance since the 2-hydroxymuconic semialdehyde hydrolase was present Enzymes. Catechol 1,2-oxygenase or catechol: oxygen 1,2-oxidoreductase (EC 1.13.1.1); catechol 2,3-oxygenase or catecho1:oxygen 2,3-oxidoredoctase (EC 1.13.1.2); NAD nucleosidase or NAD glycohydrolase (EC 3.2.2.6). 21 Eur. J. Blochem., Vol.28 in only very low uninducible levels. I n NCIB 9816 all the enzymes of the 4-oxalocrotonate branch are present [4] and again it has been proposed that catechol is metab...

show abstract

Section: Discussionsupporting

confidence: 70%