Synthetic Macromolecular Inhibitors of Human Leukocyte Elastase. 2. Effect of Loading of a Peptidyl Carbamate Inhibitor and Molecular Size of Polymer Backbone on its Inhibitory Capacity

Abstract

Several macromolecular inhibitors of human leukocyte elastase (HLE) were prepared by covalently bonding a low molecular weight HLE inhibitor peptidyl carbamate, p-nitrophenyl-N-[succinyl-L-alanyl-L-ananyl-L-prolylmethyl]-N-isopropyl carbamate 1, with the neutral hydrophilic polymer, poly-α,β-[N-(2-hydroxyethyl)-D, L-aspartamide], PHEA 2. These novel polymeric compounds differed in the molecular size of their PHEA polymer backbone and the extent of loading of the peptidyl carbamate, (PC). They were shown to efficiently inhibit HLE (K_i = 97 to 12.8 nM) as intact macromolecular entities and were found to be more stable to hydrolysis than the non-polymer bound low molecular weight inhibitor 1.

The inhibition of HLE by the novel macromolecular inhibitors was found to be noncompetitive and reversible, proceeding via slow formation of inhibitor-enzyme complex. The effect of loading of 1 and molecular size of the PHEA 2 polymer on enzymatic parameters K_i, k_on and k_off is discussed and a possible mechanism of inhibition is presented.

Key Words: :

• Human leukocyte elastase (HLE)
• peptidyl carbamate; p-nitrophenyl-N-[succinyl-L-aIanyl-L-alanyl-L-prolylmethyl]-N-isopropylcarbamate
• enzyme-inhibitor complex
• inhibitory capacity
• poly-α, β[N-(2-hydroxyethyl)-D, L-aspartamide]
• PHEA
• polysuccinimide
• effect of loading
• molecular size
• polymeric inhibitor
• mechanism of inhibition.