A purified pectate lyase isozyme derived from Erwinia chrysanthemi induced rapid net K(+) efflux and H(+) influx in suspension-cultured tobacco cells. Comparable fluxes of other ions (Na(+), Cl(-)) were not observed. The K(+) efflux/H(+) influx response began within 15 minutes after addition of enzyme to cell suspensions and continued for approximately 1 hour after which cells resumed the net H(+) efflux exhibited prior to enzyme treatment. The response was not prolonged by a second enzyme dose 1 hour after the first. The K(+)/H(+) response was characterized by saturation at low enzymic activity (2 x 10(-3) units per milliliter), and inhibition by the protonophore, carbonyl cyanide m-chlorophenylhydrazone, and was not associated with membrane leakiness caused by structural cell wall damage. The total K(+) loss and H(+) uptake induced by enzyme was one-fourth to one-third that induced by Pseudomonas syringae pv. pisi and did not reduce cell viability. These results indicate that pectate lyase induces a K(+) efflux/H(+) influx response in tobacco similar to but of shorter duration than that induced by P. syringae pv. pisi during the hypersensitive response. Pectate lyase or other cell wall degrading enzymes may therefore influence the induction of hypersensitivity.