Purification of a nickel-containing urease from the rumen anaerobe Selenomonas ruminantium.
Urease was purified 592-fold to homogeneity from the anaerobic rumen bacterium Selenomonas ruminantium. The urease isolation procedure included a heat step and ion-exchange, hydrophobic, gel filtration, and fast protein liquid chromatography. The purified enzyme exhibited a Km for urea of 2.2 +/- 0.5 mM and a Vmax of 1100 mumol of urea min-1 mg-1. The molecular mass estimated for the native enzyme was 360,000 +/- 50,000 daltons, whereas a subunit value of 70,000 +/- 2,000 daltons was determined. These results are in contrast to the findings of Mahadevan et al. (Mahadevan, S., Sauer, F. D., and Erfle, J. D. (1977) Biochem. J. 163, 495-501) in which isolated rumen urease was reported to be one-third this size (Mr 120,000-130,000) and to catalyze urea hydrolysis at a maximum velocity of only 53 mumol min-1 mg-1. S. ruminantium urease contained 2.1 +/- 0.4 nickel ions/subunit, comparable to the nickel content in jack bean urease (Dixon, N.E., Gazzola, C., Blakeley, R.L., and Zerner, B. (1975) J. Am. Chem. Soc. 97, 4131-4133). Thus, the active site of bacterial urease is very similar to that found in the plant enzymes.
R P
RP
Hausinger
D000693:Anaerobiosis; D000818:Animals; D002417:Cattle; D006089:Gram-Negative Anaerobic Bacteria / Q000201:enzymology*; D007700:Kinetics; D046911:Macromolecular Substances; D008970:Molecular Weight; D009532:Nickel / Q000032:analysis*; D012417:Rumen / Q000382:microbiology*; D014510:Urease / Q000302:isolation & purification* / Q000378:metabolism
D046911:Macromolecular Substances; D009532:Nickel; D014510:Urease