Nickel-content of urease from Bacillus pasteurii

Area of Science:

• Enzymology
• Biochemistry
• Microbiology

Background:

• Urease enzymes are critical in the urea cycle and nitrogen metabolism.
• Bacillus pasteurii is known for its urease production, but its enzyme's structure and cofactors require detailed characterization.

Purpose of the Study:

• To purify and characterize urease from Bacillus pasteurii.
• To determine the enzyme's molecular properties and cofactor composition, specifically investigating nickel content.

Main Methods:

• Purification of urease using techniques like ion-exchange and affinity chromatography.
• Homogeneity assessment via isoelectric focusing.
• Molecular mass determination using SDS electrophoresis.
• Nickel cofactor identification using radioactive 63Ni and atomic absorption spectrometry.

Main Results:

• Urease was purified 34-fold with high specific activity (996.5 mumol urea min-1 mg-1).
• The enzyme is a homodimer with a native molecular mass of 230,000 Da, composed of 65,500 Da subunits.
• Each subunit contains one atom of nickel, indicating a tetrameric structure with four nickel atoms per enzyme molecule.

Conclusions:

• Bacillus pasteurii urease is a nickel-containing enzyme essential for its catalytic function.
• The enzyme's structure, comprising four identical nickel-bound subunits, provides insights into urease mechanisms.