Hiroto Kondo

Oryzacystatins exhibit growth-inhibitory and lethal effects on different species of bean insect pests, Callosobruchus chinensis (Coleoptera) and Riptortus clavatus (Hemiptera).

Oryzacystatins I and II, cysteine proteinase inhibitors in rice seeds, caused growth retardation of different species of bean insect pests, Callosobruchus chinensis (Coleoptera) and Riptortus clavatus (Hemiptera), when added to their diets at concentrations of 0.3-0.5% (w/w). At concentrations of up to 1%, almost all insects died. Our results suggest the usefulness of cystatin for insect pest control and also the critical role of cysteine proteinase in the digestive events of insects.

Inhibitory effect of oryzacystatins and a truncation mutant on the replication of poliovirus in infected Vero cells

Poliovirus, a picornavirus family member, requires the processing of its poly‐protein by its own cysteine proteinase for replication. Oryzacystatin‐I and oryzacystatin‐II, proteinaceous cysteine proteinase inhibitors (cystatins) of rice seed origin, were found to inhibit the replication of poliovirus effectively in infected Vero cells in vitro. Truncated oryzacystatin‐I, which lacks the NH2‐terminal 25 amino acid residues of the intact protein, is an even more effective inhibitor, eliciting its effect at concentrations of less than 0.23 nmol/ml. The low molecular weight cysteine proteinase inhibitors, E‐64, E‐64C and loxistatin, showed no anti‐viral effect at any concentration investigated.