The inactivation of one- and two-chain forms of tissue plasminogen activator by a series of peptidyl chloromethyl ketones.

The inhibition of one- and two-chain forms of tissue-type plasminogen activator by a series of peptide derivatives of arginine chloromethyl ketone was studied. Both forms of the enzyme were inhibited by such reagents at varying rates, dependent on the peptide sequence of the inhibitor. The order of relative effectiveness of the inhibitors was the same for both one- and two-chain tissue plasminogen activator. However, an approximately ten to twenty-fold higher concentration of reagent was required with the one-chain activator to produce similar rates of inactivation. It appears that the specificity of the active sites of the one and two chain forms of tissue plasminogen activator are very similar. It is suggested that the differences in enzymatic properties of the two forms are due mainly to effects on binding (Ki) rather than on the rate of alkylation and inhibition (k2).