An extracellular poly(3-hydroxybutyrate) depolymerase from Alcaligenes faecalis.
A strain of Alcaligenes faecalis T1, which was isolated from activated sludge, excreted an extracellular poly(3-hydroxybutyrate) depolymerase as it grew in a medium containing poly(3-hydroxybutyrate) as the sole carbon source. The molecular weight of the enzyme, purified from the culture medium to electrophoretic homogeneity, was 48 000 as determined by Sephadex G-100 filtration, and 50 000 by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate. The pH optimum for the enzyme reaction was 7.5. The purified enzyme depolymerized poly(3-hydroxybutyrate) purified from Zoogloea ramigera 1-16-M, but did not attack the bacterial native poly(3-hydroxybutyrate)-containing granules. Km values were 13.3 micrograms/ml (= 0.78 microM, based on an estimated average molecular weight of 17 000) for poly(3-hydroxybutyrate) and 5.4 mM for the trimeric ester of D(--)-3-hydroxybutyric acid. Analysis of hydrolytic products of poly(3-hydroxybutyrate), several oligomeric esters of D(--)-3-hydroxybutyric acid, and the methyl ester of the trimeric ester indicated that the enzyme hydrolyzed these substrates from the free hydroxyl terminus, releasing D(--)-3-hydroxybutyrate dimer units one at a time.
D000421:Alcaligenes / Q000201:enzymology* / Q000254:growth & development; D001426:Bacterial Proteins / Q000302:isolation & purification*; D002265:Carboxylic Ester Hydrolases / Q000302:isolation & purification* / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology; D055598:Chemical Phenomena; D002621:Chemistry; D006868:Hydrolysis; D007700:Kinetics; D013379:Substrate Specificity
D001426:Bacterial Proteins; D002265:Carboxylic Ester Hydrolases; C022417:poly-beta-hydroxybutyrate depolymerase