title: Characterization of esterases produced by a ruminal bacterium identified as Butyrivibrio fibrisolvens.
abstract: An obligately anaerobic ruminal bacterial isolate was selected from 18 tributyrin-degrading isolates and identified as Butyrivibrio fibrisolvens strain 53. The culture in late exponential phase contained enzymes which could be released by sonic disruption. These enzymes degraded substrates at a rate in the order 1-naphthyl acetate (NA) > 1-naphthyl butyrate > 1-naphthyl propionate but did not degrade 1-naphthyl palmitate or 1-naphthyl phosphate. The enzymes on NA were neither stimulated nor inhibited by CoCl(2), MgCl(2), and MnCl (each varied from 10(-6) to 10(-4) M). CaCl at 10(-3) M stimulated esterase activity by 16%. Aliphatic substrates were hydrolyzed at a rate in the order triacetin > tributyrin > tripropionin, and ethyl acetate > ethyl formate. Similarly, aromatic fluorescein diesters were degraded at a rate in the order acetyl > propionyl > caproyl > butyryl > capryl > lauryl. Polyacrylamide gel electrophoretic zymograms indicated that the enzyme composite contained cathodally migrating bands. By column chromatography, these enzymes were separated into six NA-degrading fractions. Fraction V contained an esterase which had an optimal temperature of 39 C, a K(m) of 7.6 x 10(-4) on NA, and a molecular weight of about 66,000. This enzyme was inhibited by paraoxon (41%, 10(-4) M), eserine (17%, 10(-2) M), NaF (17%, 10(-2) M), and diisopropyl fluorophosphate (62%, 10(-4) M) but not by 1-naphthyl N-methyl carbamate at 8.4 x 10(-4) M.
mesh_terms: D000693:Anaerobiosis; D000818:Animals; D001419:Bacteria / Q000145:classification / Q000201:enzymology* / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D002417:Cattle; D002474:Cell-Free System; D002499:Centrifugation, Density Gradient; D002845:Chromatography; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D004950:Esterases / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism; D004952:Esters / Q000378:metabolism; D005223:Fats / Q000378:metabolism; D008049:Lipase / Q000378:metabolism; D008970:Molecular Weight; D012417:Rumen / Q000382:microbiology*; D013696:Temperature
chemical_list: D004952:Esters; D005223:Fats; D004950:Esterases; D008049:Lipase