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PubMed1976

Regulation of arginine and pyrimidine biosynthesis in Pseudomonas putida.

Repression of biosynthetic enzyme synthesis in Pseudomonas putida is incomplete even when the bacteria are growing in a nutritionally complex environment. The synthesis of four of the enzymes of the arginine biosynthetic pathway (N-acetyl-alpha-glutamokinase/N-acetylglutamate-gamma-semialdehyde dehydrogenase, ornithine carbamoyltransferase and acetylornithine-delta-transaminase) could be repressed and derepressed, but the maximum difference observed between repressed and derepressed levels for any enzyme of the pathway was only 5-fold (for ornithine carbamoyltransferase). No repression of five enzymes of the pyrimidine biosynthetic pathway (aspartate carbamoyltransferase, dihydro-orotase, dihydro-orotate dehydrogenase, orotidine-5'-phosphate pyrophosphorylase and orotidine-5'-phosphate decarboxylase) could be detected on addition of pyrimidines to minimal asparagine cultures of P. putida A90, but a 1-5- to 2-fold degree of derepression was found following pyrimidine starvation of pyrimidine auxotrophic mutants of P. putida A90. Aspartate carbamoyltransferase in crude extracts of P. putida A90 was inhibited in vitro by (in order of efficiency) pyrophosphate, CTP, UTP and ATP, at limiting but not at saturating concentrations of carbamoyl phosphate.

Aldehyde Oxidoreductases↗
PubMed1986

Female-predominant expression of testosterone 16 alpha-hydroxylase ("I"-P-450(16)alpha) and its repression in strain 129/J.

Using specific testosterone 16 alpha-hydroxylase activity as the basis for selection of fractions during purification, the cytochrome P-450 ("I"-P-450(16)alpha) has been isolated from livers of phenobarbital-treated 129/J female mice [K. Devore, N. Harada, and M. Negishi (1985) Biochemistry, 24, 5632-5637]. An antibody elicited in rabbits to "I"-P-450(16)alpha was used to determine the amount of hepatic microsomal 16 alpha-hydroxylase activity due to "I"-P-450(16)alpha in untreated females and males of the two mouse strains, 129/J and BALB/cJ. The activities inhibited were 0.03 and 0.3 nmol/min/mg protein in the 129/J and BALB/cJ females, respectively. No significant level of "I"-P-450(16)alpha-dependent activity was detected in the microsomes from males of either mouse strain. Immunoblotting of microsomal proteins with the antibody to "I"-P-450(16)alpha revealed approximately a 10-fold greater amount of a 54-kDa protein in the microsomes from BALB/cJ than from 129/J females (0.03 and 0.26 pmol/micrograms protein, respectively). A cDNA clone (R17) for phenobarbital-inducible rat cytochrome P-450 selected "I"-P-450(16)alpha mRNA of mice, indicating a high degree of homology between the mRNAs of mouse "I"-P-450(16)alpha and phenobarbital-inducible rat cytochrome P-450s. Northern and dot hybridization of total mouse liver poly(A)+ RNA with the R17 cDNA probe indicated that the specific content of the hybridizable mRNA was more than 10 times higher in BALB/cJ females than in males, and that the mRNA level in female 129/J mice was very similar to that of 129/J and BALB/cJ males. The repression of "I"-P-450(16)alpha in 129/J females was inherited as an autosomal recessive trait in 129/J and BALB/cJ pairs as indicated by the levels of mRNA in female F1 offspring and the "I"-P-450(16)alpha-dependent hydroxylase activity. Female and male mice of eight more inbred strains (AKR/J, DBA/2J, C57BL/6J, C3H/HeJ, NZB/J, A/J, CBA/CaJ, and P/J) were tested for levels of mRNA. The results showed that the levels of mRNA were always 5- to 10-fold greater in the females than in the corresponding males, although there was some variation in the mRNA content in the males from the different strains. 129/J females appear to be a genetic variant where the female-predominant expression of the mRNA is repressed.

Animals↗