Purification and characterization of rat urinary esterase A1

Area of Science:

• Biochemistry
• Enzymology
• Urology

Background:

• Male rat urine contains multiple esterolytic enzymes, including esterase A1, esterase A2, and kallikrein.
• Understanding the specific properties and origins of these enzymes is crucial for elucidating their physiological functions.

Purpose of the Study:

• To isolate and purify esterase A1 from male rat urine.
• To characterize the biochemical properties of purified esterase A1.
• To differentiate esterase A1 from other urinary enzymes like esterase A2 and kallikrein.

Main Methods:

• Enzyme purification using ammonium sulfate fractionation, ion exchange chromatography, hydrophobic chromatography, and gel filtration.
• Homogeneity assessment via polyacrylamide gel electrophoresis (PAGE).
• Molecular weight determination using SDS-PAGE and gel filtration.
• Enzyme kinetics (pH optimum, Km) and substrate specificity analysis.
• Inhibition studies with soybean trypsin inhibitor and aprotinin.
• Immunodiffusion analysis using antiserum against esterase A1.

Main Results:

• Esterase A1 was purified to apparent homogeneity with a molecular weight of approximately 27,000-30,000 Da.
• The enzyme exhibited specificity for arginine methyl esters over lysine methyl esters, with an optimal pH of 8.0 and a Km of 11.8 mM for tosyl-arginine methyl ester.
• Esterase A1 activity was inhibited by soybean trypsin inhibitor but not aprotinin.
• Immunodiffusion confirmed esterase A1 is distinct from esterase A2 and kallikrein and is present in bladder urine but not plasma or ureter urine.

Conclusions:

• Rat urinary esterase A1 is a distinct enzyme from esterase A2 and kallikrein.
• Esterase A1 is likely produced by the accessory sex glands and secreted into the urine via the spermiduct.