Ribonuclease(RNase) inhibitor has been known to specifically inhibit RNase known to be involved in carcinogenesis and suppression of cancer. In order to understand interactions between RNase and RNase inhibitor in serum of patients with acute lymphocytic leukemia(ALL), the serum was pretreated with parahydroxymer-curibenzoate(PHMB) and then was chromatographed to remove RNase inhibitor from RNase-RNase inhibitor complex. Properties of the inhibitor released RNase thus obtained from the ALL serum pretreated with PHMB were compared with those from the ALL serum without PHMB pretreatment and with those from the conrol serum.
RNases in the ALL serum without PHMB pretreatment were separated by a DEAE-cellulose column chromatography into five isozymes (free RNase isozyme I-Ⅴ), of which three isozyme activities were greater than those in the control serum, suggesting that free RNase isozymes I, Ⅱ and Ⅲ in the ALL serum were activated. RNase inhibitor activity was higher in all of the four free RNase isozymes(Ⅱ-Ⅴ) except for the isozyme I, being highest in the isozyme Ⅴ.
RNases in the ALL serum with PHMB pretreatment were also separated by the chromatography into five isozymes(inhibitor released RNase isozyme I-Ⅴ), of which the inhibitor released RNase isozyme I activity being markedly higher than free RNase isozyme I activity from ALL serum without PHMB pretreatment. The RNase inhibitor acitivity was greatly reduced in each of the isozymes isolated from the serum with PHMB pretreatment. The results indicated that RNases in the ALL serum pretreated with PHMB were present in the state of inhibitor released RNase isozyme, accumulating in the isozyme I.
Activities of all of the free RNase isozymes separated from the ALL serum except for the isozyme V were higher toward poly C than toward RNA as substrate, ratio of RNA/poly C being lower, suggesting the nature of secretory type of RNase. Ratio of RNA/poly C in the isozyme V from the ALL serum was higher than that from the control serum and was close 1.0, suggesting the nature of nonsecretory type of RNase. The results indicated that the free RNase isozyme V isolated from the ALL serum was different from that from the control serum. Ratio of RNA/poly C of each of the inhibitor released RNase isozyme activity from the ALL serum with PHMB pretreatment was similar to each of those from the control serum, except for the isozyme I. Ratio of RNA/poly C of inhibitor released RNase isozyme I activity from the ALL serum was greater than that of inhibitor released RNase isozyme I activity from the control serum and that of free RNase isozyme I activity from the ALL serum.
These results suggested that the inhibitor relesed RNase isozymes isolated from the ALL serum were different in nature from the free RNase.
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