title: Isolation and properties of free and immobilized beta-galactosidase from the psychorotrophic enterobacterium Buttiauxella agrestis (strain NC4).
abstract: A study of the beta-galactosidase produced by the psychrotrophic bacterium Buttiauxella agrestis has been carried out. This micro-organism was isolated from raw milk and the enzyme isolated using standard methods. Molecular mass was estimated to be 515 kDa. The isoelectric point was close to 4.45. Optimum pH was 7.25. Maximal activity was observed at 50 degrees C and activation energy was estimated to be 39.1 kJ mol-1. Lactose enhanced thermal stability. Using p-nitrophenyl-beta-D-galactopyranoside as the substrate, the Km was 11 mumol l-1 and Vmax was 85 U mg-1 protein. beta-Mercaptoethanol and ethanol were inhibitors; glycerol acted as a complex effector. The enzyme required divalent cations for activity while it was inhibited by EDTA. When the enzyme was immobilized in diethyl aminoethylcellulose the optimum pH of activity was 8. Km was 47 mumol l-1 and Vmax was 96 U mg-1 protein.
authors.affiliation: Departamento de Bioquimica y Biología Molecular, Facultad de Ciencias, Universidad del País Vasco/Euskal Herriko Unibertsitatea, Bilbao, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Amarita
authors.forename: F
authors.initials: F
authors.lastname: Alkorta
authors.forename: M
authors.initials: M
authors.lastname: Lescan du Plessix
authors.forename: T
authors.initials: T
authors.lastname: Cantabrana
authors.forename: C
authors.initials: C
authors.lastname: Rodriguez-Fernandez
mesh_terms: D000438:Alcohols / Q000494:pharmacology; D000818:Animals; D002412:Cations / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004755:Enterobacteriaceae / Q000201:enzymology*; D004789:Enzyme Activation; D004800:Enzymes, Immobilized; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008892:Milk / Q000382:microbiology; D013696:Temperature; D001616:beta-Galactosidase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D000438:Alcohols; D002412:Cations; D004800:Enzymes, Immobilized; D004492:Edetic Acid; D001616:beta-Galactosidase