SERINE PROTEINASE LIKE ACTIVITY IN APOLIPOPHORIN III FROM THE HEMOLYMPH OF DESERT LOCUST, S chistocerca gregaria

• Published in: Archives of insect biochemistry and physiology 2012-06, Vol.80 (1), p.26-41
• Main Authors: Malik, Zulfiqar A., Amir, Sumaira, Venekei, István
• Format: Article
• Language: English
• ISSN: 0739-4462; 1520-6327
• DOI: 10.1002/arch.21020

Apolipophorin III (apoLp‐III) has been known as a lipid transport protein of insects. Recent studies indicated the involvement of apoLp‐III in immune reactions and in the control of cell destruction, but no enzymatic activity has so far been detected. In the present study, a protease from the hemolymph of S chistocerca gregaria was purified to homogeneity and its enzymatic activity was examined. Identity as chymotrypsin‐like proteinase was established by its high affinity toward bulky aromatic substrates and its catalytic specificity for amide or ester bonds on the synthetic substrates, S uc‐ A la‐ A la‐ P ro‐ X aa‐ AMC (where X aa was P he, T yr, T rp, and L ys, and AMC is 7‐amino‐4‐methyl‐coumarin) and thiolbenzyl ester substrate S uc‐ A la‐ A la‐ P ro‐ P he‐ SB zl. The sensitivity for serine protease and chymotrypsin‐specific covalent inhibitors, PMSF , TPCK , and noncovalent inhibitors SGCI , showed that it is a chymotrypsin‐like proteinase. It showed its maximum activity at pH 8.0 and 55°C for the hydrolysis of S uc‐ A la‐ A la‐ P ro‐ T yr‐ AMC . According to similarities in the amino terminal sequence, molar mass (19 kDa) and retention on reversed‐phase analytical high-performance liquid chromatography (HPLC) column , this protein is S . gregaria homologue of L ocusta migratoria apoLp‐III. Our data suggest that apoLp‐III also has an inherent proteolytic activity. Results indicated that S . gregaria apoLp‐III is a good catalyst and could be used as a biotechnological tool in food processing and in agricultural biotechnology .