A Stable Serine Protease, Wrightin, from the Latex of the Plant Wrightia tinctoria (Roxb.) R. Br.: Purification and Biochemical Properties

• Published in: Journal of agricultural and food chemistry Vol. 56; no. 4; pp. 1479 - 1487
• Main Authors: Tomar, Ritu, Kumar, Reetesh, Jagannadham, M. V
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 27.02.2008
• Subjects: Apocynaceae - enzymology; Biological and medical sciences; Chromatography, Ion Exchange - methods; enzyme activity; enzyme inhibitors; Enzyme Stability; Food Chemistry/Biochemistry; Food industries; Fundamental and applied biological sciences. Psychology; glycosylated; Hydrogen-Ion Concentration; Hydrolysis; Isoelectric Point; Kinetics; Latex; Molecular Weight; physicochemical properties; Plant protease; protein hydrolysates; proteins; Serine Endopeptidases - chemistry; Serine Endopeptidases - isolation & purification; Serine Endopeptidases - metabolism; serine protease; serine proteinases; Substrate Specificity; Temperature; Wrightia; Wrightia tinctoria; wrightin; wrightin; glycosylated; Wrightia tinctoria; serine protease; Plant protease; Purification; Enzyme; Serine; Properties; Latex; Peptidases; Aminoacid; Hydrolases
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf0726536

Today proteases have become an integral part of the food and feed industry, and plant latex could be a potential source of novel proteases with unique substrate specificities and biochemical properties. A new protease named “wrightin” is purified from the latex of the plant Wrightia tinctoria (Family Apocynaceae) by cation-exchange chromatography. The enzyme is a monomer having a molecular mass of 57.9 kDa (MALDI-TOF), an isoelectric point of 6.0, and an extinction coefficient (ϵ1% 280) of 36.4. Optimum activity is achieved at a pH of 7.5–10 and a temperature of 70 °C. Wrightin hydrolyzes denatured natural substrates such as casein, azoalbumin, and hemoglobin with high specific activity; for example, the K m value is 50 µM for casein as substrate. Wrightin showed weak amidolytic activity toward l-Ala-Ala-p-nitroanilide but completely failed to hydrolyze N-α-benzoyl-dl-arginine-p-nitroanilide (BAPNA), a preferred substrate for trypsin-like enzymes. Complete inhibition of enzyme activity by serine protease inhibitors such as PMSF and DFP indicates that the enzyme belongs to the serine protease class. The enzyme was not inhibited by SBTI and resists autodigestion. Wrightin is remarkably thermostable, retaining complete activity at 70 °C after 60 min of incubation and 74% of activity after 30 min of incubation at 80°. Besides, the enzyme is very stable over a broad range of pH from 5.0 to 11.5 and remains active in the presence of various denaturants, surfactants, organic solvents, and metal ions. Thus, wrightin might be a potential candidate for various applications in the food and biotechnological industries, especially in operations requiring high temperatures.