ELEVATED PROTEINASE ACTIVITIES IN MOUSE LUNG-TUMORS QUANTITATED BY SYNTHETIC FLUOROGENIC SUBSTRATES

Proteinase activities in malignant and normal lung tissues were measured using two synthetic substrates that consist of a fluorophor coupled to a peptide moiety. They hydrolysis of CBZ-Val-Lys-Lys-Arg-4-methoxy-2-naphthylamide and CBZ-Val-Lys-Lys-Arg-4-methoxy-2-naphthylamide were studied in homogenates of two types of mouse lung tumors, the Lewis lung tumor of the C57 black mouse and the KHT tumor of the C3H mouse. The activity of CBZ-Val-Lsy-Lsy-Arg-4-methoxy-2-naphthylamide hydrolysis had a pH optimum of 6.3 and Km of 2.1 x 10-4 M, required a thiol activator, and was inhibited by leupeptin suggesting the activity of a cathepsin B-like enzyme. The activity of BZ-Gly-Gly-Arg-4-methoxy-2-naphthylamide hydrolysis had a pH optimum of 6.7 and Km of 3 x 105 M. Lung tumor homogenates contained higher hydrolytic activities or both substrates than normal lung homogenates.