Adenine Phosphoribosyltransferase in Mycoplasma mycoides and Escherichia coli
AUTOR(ES)
Sin, Iris L.
RESUMO
Some kinetic properties of the adenine phosphoribosyltransferases from Escherichia coli and Mycoplasma mycoides have been studied. For the E. coli enzyme, Michaelis constants for adenine and 5-phosphoribosyl-1-pyrophosphate (PRPP) are 1.3 and 10 μm, respectively. Adenosine monophosphate, the most effective nucleotide inhibitor, inhibits competitively with respect to PRPP, the inhibition constant being 26 μm. The M. mycoides enzyme has more complex kinetics. The response to increasing PRPP concentration is sigmoidal, the degree of sigmoidality depending on both the concentration of adenine and the pH. At low PRPP levels, high concentrations of adenine are inhibitory. Guanosine monophosphate is the most effective inhibitor, being inhibitory at all pH values, but other nucleotides have been found to activate at pH 7 and inhibit at pH 8. The elution profile of the M. mycoides enzyme from Sephadex suggests an association of enzyme subunits in the presence of PRPP. This is consistent with the observed kinetics if the associated form has increased stability and activity.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=251430Documentos Relacionados
- Comparative Studies of Antigens from Mycoplasma mycoides and Escherichia coli
- Genetic and Serological Analysis of Lipoprotein LppA in Mycoplasma mycoides subsp. mycoides LC and Mycoplasma mycoides subsp. capri
- Reduced nicotinamide adenine dinucleotide oxidase activity in membranes and cytoplasm of Acholeplasma laidlawii and Mycoplasma mycoides subsp. capri.
- Studies on Mycoplasma mycoides subsp. mycoides (LC) in lambs and calves.
- Enzymes of Pyrimidine Metabolism in Mycoplasma mycoides subsp. mycoides
