title: Catabolic pathway for aerobic degradation of lactate by Actinomyces naeslundii.
abstract: The aerobic metabolism of lactate by oral Actinomyces was studied. Six of 7 strains of Actinomyces naeslundii increased their growth in the presence of lactate under aerobic conditions. Washed cells grown on lactate aerobically degraded lactate and pyruvate to acetate with a concomitant consumption of oxygen. In the presence of catalase, the molar ratios of oxygen consumed to acetate produced were 1 for lactate degradation and 0.5 for pyruvate degradation. The enzymatic activities found in cell extracts revealed that lactate could be converted to pyruvate by NAD-independent lactate dehydrogenase (iLDH) and further to acetyl CoA by pyruvate dehydrogenase (PDH). The acetyl CoA formed could be metabolized into acetate by phosphotransacetylase (PTA) and acetate kinase (AK) with the formation of ATP. These results indicate that A. naeslundii metabolizes lactate into acetate by the sequential enzymatic reactions iLDH, PDH, PTA and AK and that hydrogens produced by iLDH and PDH are transferred to oxygen. The activity of lactate degradation and oxygen consumption may modify the environmental conditions of dental plaque.
authors.affiliation: Department of Oral Biochemistry, Tohoku University, School of Dentistry, Sendai, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Takahashi
authors.forename: T
authors.initials: T
authors.lastname: Yamada
mesh_terms: D000084:Acetate Kinase / Q000378:metabolism; D000190:Actinomyces / Q000201:enzymology / Q000378:metabolism*; D000332:Aerobiosis; D002374:Catalase / Q000378:metabolism; D003773:Dental Plaque / Q000382:microbiology; D017753:Ecosystem; D005947:Glucose / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D007773:Lactates / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D010101:Oxygen Consumption; D010709:Phosphate Acetyltransferase / Q000378:metabolism; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism; D011773:Pyruvates / Q000378:metabolism
chemical_list: D007773:Lactates; D011768:Pyruvate Dehydrogenase Complex; D011773:Pyruvates; D009243:NAD; D007770:L-Lactate Dehydrogenase; D002374:Catalase; D010709:Phosphate Acetyltransferase; D000084:Acetate Kinase; D005947:Glucose