Cathepsin Y (a novel thiol enzyme) produces kinin potentiating peptide from the component protein of rat plasma.

Rat spleen cathepsin Y (a novel enzyme) that produces bradykinin (BK) potentiating peptide (BPP) from rat plasma was isolated, characterized and its amino acid sequence was deduced from cDNA cloned by reverse transcription-polymerase chain reaction (RT-PCR). We propose the name cathepsin Y for this enzyme considering its origin, characteristics and the amino acid sequence. BPP potentiates not only BK but also lysyl-BK (lysBK) and T-kinin (TK) action on uterus contraction. The structure of BPP is Pro-Pro-Pro-Leu-Gly-Pro-Gly-Ser. The magnitude of the potentiation of BK activity by synthesized BPP was seven-fold when equivalent quantities added to BK and 23-fold when the level is doubled. The precursor proteins that produce BPP by the action of cathepsin Y are eluted into two fractions when the heated plasma was applied to a negative ion exchange column. Structure relationships between these two proteins are now under investigation. In this paper, we report on the characteristics and the amino acid sequence of rat spleen cathepsin Y, its structure and the potentiating activity of BPP, and isolation of the precursor protein.