Malate dehydrogenase and glucose-6-phosphate dehydrogenase, key markers for studying the genetic diversity of Actinobacillus actinomycetemcomitans.
Cell-free extracts of strains belonging to the 5 serotypes of A. actinomycetemcomitans were screened for several enzymes. Enzymes representative of the pentose phosphate pathway/hexose monophosphate shunt and the TCA cycle were present. Of these glucose-6-phosphate dehydrogenase (G6PDH) and malate dehydrogenase (MDH) were the most readily detected and stable. MDH and G6PDH retained more than 50% of their activities at alkaline pHs (10-11) for up to 6 h and 3 h at 25 degrees C, respectively, while at pH 6.5, 50% of their activities were lost within 2-3 h. The Km for malate oxidation catalysed by MDH was 5.8 x 10(-4) M while that for glucose-6-phosphate oxidation was 2.0 x 10(-4) M. The pH optima for MDH and G6PDH oxidation activities were 10 and 9.5, respectively. Among the 5 designated serotypes of A. actinomycetemcomitans three groups were delineated by multilocus enzyme electrophoresis using MDH and G6PDH.
Department of Microbiology, Eastman Dental Institute, University of London, UK.
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Shah
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Andrews
D016976:Aggregatibacter actinomycetemcomitans / Q000201:enzymology / Q000235:genetics*; D015415:Biomarkers; D004586:Electrophoresis; D014644:Genetic Variation; D005954:Glucosephosphate Dehydrogenase / Q000302:isolation & purification*; D008291:Malate Dehydrogenase / Q000302:isolation & purification*; D013045:Species Specificity
D015415:Biomarkers; D008291:Malate Dehydrogenase; D005954:Glucosephosphate Dehydrogenase