Description
General description
Subunit molecular weight: ~90,770
Composed of six subunits with total molecular weight: ~544,620
Urease of jack bean (Canavalia ensiformis), a hexamer of a single chain of 840 amino acid residues, is found in plants, bacteria, fungi, algae, and soil. It is considered the first nickel-containing enzyme and the first enzyme to be crystallized. Ureases exist in several isoforms, some are jack bean urease (JBURE-I), canatoxin (CNTX), and JBURE-IIB. JBURE-I is more abundant than the other two isoforms. Ureases are found in mature seeds.
Application
Urease from Canavalia ensiformis (Jack bean) has been used:
to assay creatine and creatine phosphate using the sample extracted from the left ventricle (LV) and septal tissue
to determine the concentration of urea in a stabilized urine sample
as one of the standards to measure the urease activity of plant extracts
Biochem/physiol Actions
In plants, ureases are essential for the bioavailability/metabolism of nitrogen in nature and defense mechanisms. Ureases are metalloenzymes that catalyze the hydrolysis of urea to release ammonia a nitrogen source for growth and carbon dioxide. They exhibit internal peptides-mediated insecticidal action and fungicidal activity.
Urease activity has been shown to be inhibited by benzpyrene following exposure to light. This inhibition was due to the effect of benzpyrene on urease′s sulfhydryl groups.
Other Notes
One micromolar unit will liberate 1.0 μmole of NH3 from urea per min at pH 7.0 at 25 °C. It is equivalent to 1.0 I.U. or 0.054 Sumner unit (1.0 mg ammonia nitrogen in 5 minutes at pH 7.0 at 20 °C)
