Publication Type
Journal Article
Journal Name
Insect Biochemistry and Molecular Biology
Publication Date
1-1-1992
Abstract
Two proteinases designated 1 and 2, purified from the gut of partially engorged female, Rhipicephalus appendiculatus have been characterized. Both proteinases hydrolysed denatured haemoglobin (Hb) at acid pH, with Michaelis constants (KM) of 1.19 g/100 ml (proteinase 1) and 0.71 g/100 ml (proteinase 2). Pepstatin competitively inhibited both proteinases, with a K1 of 1.7 nM (proteinase 2). Both proteinases were also inhibited by 1 mM phenylmethylsulphonyl fluoride (PMSF). The pH optimum for proteinase 1 was 3.0, with a smaller but distinct second peak at pH 4.6. For proteinase 2, peak activity was at pH 2.6 with a second smaller peak at pH 5.0. Both enzymes rapidly lost activity at 50°C and above. Thermal inactivation and inhibition by pepstatin were pH-dependent for proteinase 2 but not for proteinase 1. On the basis of these results, proteinases 1 and 2 have been classified as aspartic proteinases. © 1992.
Keywords
aspartic proteinases, cathepsin D, digestive enzymes, Rhipicephalus appendiculatus
Recommended Citation
Vundla, W., Brossard, M., Pearson, D., & Labongo, V. (1992). Characterization of aspartic proteinases from the gut of the tick, Rhipicephalus appendiculatus neuman. Insect Biochemistry and Molecular Biology, 22 (4), 405-410. https://doi.org/10.1016/0965-1748(92)90079-T