Purification and characterization of a novel trypsin-like protease from green-seeded chickpea (Cicer arientum)

ABSTRACT

The present study describes the purification and physicochemical and biochemical characterization of trypsin-like protease from green-seeded chickpea (Cicer arientum). The crude extract of chickpea trypsin (CpT) was obtained by homogenization followed by differential ammonium sulfate precipitation. The CpT was purified by ion-exchange chromatography on diethylaminoethyl (DEAE) column, pre-equilibrated with 20 mM tris-CaCl₂ buffer (pH 8.2) with a flow rate of 0.5 mL min⁻¹. The molecular weight and purity of ∼23 kDa of CpT were determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Activity of protease was determined using Nα-benzoyl-DL-arginine-p-nitroanilide as chromogenic substrate and CpT purified showed a specific inhibitor activity of 26978.7697 U mg⁻¹, fold purity of 9.8, and the yield of 70.2%. The characterization was performed for thermal stability, pH profile, and effect of various inhibitors on enzymatic activity. The protein isolated showed stability in the neutral to mild alkaline pH range and thermostability up to 50°C. CpT confirmed its serine nature as it was appreciably inhibited by serine protease inhibitors (maximum 6%), whereas metalloprotease inhibitors barely affected the activity of the enzyme (85%). To the best of our knowledge, it is first reported on purification of protease with trypsin-like properties, from this source.

Abbreviations:

• Nα-benzoyl-DL-arginine-p-nitroanilide
• BAPNA: Cajanus cajan trypsin inhibitor: CCTI
• chickpea trypsin: CpT
• LBTI: lima bean trypsin inhibitor
• phenylmethyl sulfonyl fluoride: PMSF
• SDS: sodium dodecyl sulfate
• TEMED: tetramethylethylenediamine

KEYWORDS:

• Cicer arientum
• enzyme
• food
• ion-exchange chromatography
• purification
• trypsin

Acknowledgments

The authors are thankful to Central Instrumentation Facility, Department of Biotechnology, JMI and Cyanobacterial Biotechnology Lab, Department of Biosciences, JMI, New Delhi to allow the access to instruments for the research work.