Properties of acetate kinase isozymes and a branched-chain fatty acid kinase from a spirochete.
Spirochete MA-2, which is anaerobic, ferments glucose, forming acetate as a major product. The spirochete also ferments (but does not utilize as growth substrates) small amounts of l-leucine, l-isoleucine, and l-valine, forming the branched-chain fatty acids isovalerate, 2-methylbutyrate, and isobutyrate, respectively, as end products. Energy generated through the fermentation of these amino acids is utilized to prolong cell survival under conditions of growth substrate starvation. A branched-chain fatty acid kinase and two acetate kinase isozymes were resolved from spirochete MA-2 cell extracts. Kinase activity was followed by measuring the formation of acyl phosphate from fatty acid and ATP. The branched-chain fatty acid kinase was active with isobutyrate, 2-methylbutyrate, isovalerate, butyrate, valerate, or propionate as a substrate but not with acetate as a substrate. The acetate kinase isozymes were active with acetate and propionate as substrates but not with longer-chain fatty acids as substrates. The acetate kinase isozymes and the branched-chain fatty acid kinase differed in nucleoside triphosphate and cation specificities. Each acetate kinase isozyme had an apparent molecular weight of approximately 125,000, whereas the branched-chain fatty acid kinase had a molecular weight of approximately 76,000. These results show that spirochete MA-2 synthesizes a branched-chain fatty acid kinase specific for leucine, isoleucine, and valine fermentation. It is likely that a phosphate branched-chain amino acids is also synthesized by spirochete MA-2. Thus, in spirochete MA-2, physiological mechanisms have evolved which serve specifically to generate maintenance energy from branched-chain amino acids.
D000084:Acetate Kinase / Q000378:metabolism*; D002412:Cations / Q000494:pharmacology; D005227:Fatty Acids / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D008970:Molecular Weight; D009711:Nucleotides / Q000494:pharmacology; D010770:Phosphotransferases / Q000378:metabolism*; D017851:Phosphotransferases (Carboxyl Group Acceptor); D013144:Spirochaetales / Q000201:enzymology*; D013379:Substrate Specificity; D013696:Temperature
D002412:Cations; D005227:Fatty Acids; D007527:Isoenzymes; D009711:Nucleotides; D010770:Phosphotransferases; D017851:Phosphotransferases (Carboxyl Group Acceptor); D000084:Acetate Kinase; C036029:branched-chain fatty-acid-kinase