Physiological and biochemical characterization of a papain inhibitor from seeds of common bean (Phaseolus vulgaris l.)

Cystatins are related proteins which share the common feature of inhibiting cysteine proteinases (i.e. papain, ficin, bromelain, etc.). These proteins were first described in animal systems. Recently the occurrence of related proteins in plant tissues has been reported. The attention towards these antimetabolites is increasing because of their possible utilization as toxic factors against pathogens, i.e. nematodes and insects. Sed cystatins could have a physiological could have a physiological role in the control of endogenous proteases during seed dormancy. The endocellular localization of these proteins and the molecular analysis of the genes could elucidate better their functions.