Partial purification of proteinase inhibitors from wounded tomato plants

Proteinase inhibitors were extracted from the upper leaves of tomato plants, Lycopersicon esculentum Mill., 48 hours after wounding single lower leaves. Inhibitors were partially purified by affinity chromatography and isoelectric focusing. Significantly higher levels of trypsin and chymotrypsin inhibitory activity were recovered from wounded plants than from unwounded controls. Several inhibitor peaks were partially resolved by isoelectric focusing of affinity column eluates from both wounded and control plants. Inhibitor activity associated with each peak was greater in wounded plants than in corresponding peaks of controls. Agar double diffusion immunological assays showed that inhibitors with basic isoelectric points (pI) of 9.5, 8.9, 8.3, 8.2, and 8.0 are serologically related to inhibitor I. Certain of these inhibitors (pI = 9.5, 8.2, and 8.0) reacted strongly with both inhibitors I and II antiserum. Three acidic proteinase inhibitors (pI = 6.5, 5.9, and 4.7), which accumulated due to wounding, also were isolated. These inhibitors are novel, since they were shown to be serologically unrelated to inhibitors I and II.