Regulation of aspartate carbamoyltransferase in Neisseria and Branhamella species.
The regulatory characteristics of aspartate carbamoyltransferase (ACTase EC 2.1.3.2) from various species of Neisseria and Branhamella have been compared. Great differences in the regulatory nature of the enzymes were observed. ATP and GTP were positive effectors in Neisseria meningitidis, N. gonorrhoeae and nine other coccal "true neisseriae" species. In four "false neisseriae" species, including Branhamella catarrhalis, no stimulating effect of ATP or GTP was observed. The rod-shaped N. elongata behaved as the "false neisseriae" in these respects, despite its taxonomic affinity to the coccal "true neisseriae" species. Except in N. meningitidis and N. lactamica, CTP had no distinct stimulatory effect. CTP had a strong inhibitory effect on ACTases from N. elongata and the "false neisseriae" species N. caviae and B. catarrhalis. The inhibitory effect of CTP was weak in N. cinerea, N. denitrificans, and the "false neisseriae" species N. ovis and N. cuniculi. Thus, there was no sharp reflection of taxonomy in the regulation of ACTase by CTP in these groups of bacteria. The apparent [S]0.5 values for aspartate and carbamoyl phosphate, displayed for five of the eighteen species, showed great variability with [S]0.5 values for aspartate ranging from 6 to 34, and for carbamoyl phosphate from 2 to 9. Treatment of the enzyme from the main test microbe N. meningitidis strain M1 by heat or para-chloromercuribenzoate (pCMB) showed that both the catalytic and the regulatory functions decreased in parallel as in the class A enzymes found in species of Pseudomonas. An estimation of the molecular weight (Mr) of the ACTase enzyme from N. meningitidis showed it to be about 295,000, which resembles the class B enzymes found in the Enterobacteriaceae.
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Kaptein W. Wilhelmsen og Frues Bakteriologiske Institutt, University of Oslo, Rikshospitalet, Norway.
D001221:Aspartate Carbamoyltransferase / Q000737:chemistry / Q000378:metabolism*; D001224:Aspartic Acid / Q000378:metabolism; D002221:Carbamyl Phosphate / Q000378:metabolism; D002729:Chloromercuribenzoates / Q000737:chemistry; D004789:Enzyme Activation; D006358:Hot Temperature; D008970:Molecular Weight; D009016:Moraxella / Q000201:enzymology*; D009343:Neisseria / Q000201:enzymology*; D009711:Nucleotides / Q000494:pharmacology; D020245:p-Chloromercuribenzoic Acid
D002729:Chloromercuribenzoates; D009711:Nucleotides; D001224:Aspartic Acid; D020245:p-Chloromercuribenzoic Acid; D002221:Carbamyl Phosphate; D001221:Aspartate Carbamoyltransferase