On the active site of elastase: Partial mapping by means of specific peptide substrates

Abstract

RNase‐S peptide as well as some related octa‐ and hexapeptides were found to be highly, reactive substrates of porcine elastase (e.g. Ala₄‐Lys‐Phe: _m = 4500 M⁻¹, k _cat = 32 sec⁻¹, C = 1.4 × 10⁵ M⁻¹ sec⁻¹). Comparison of the various peptides led to the conclusion that the active site of porcine elastase is composed of 6–7 subsites (c.f. [1]). Preliminary mapping shows that subsites S₂, S′₁ and S′₂ have hydrophobic character. Occupation of subsite S₄ by the substrate is important for efficient hydrolysis. Binding at this subsite was found to be stereospecific.