Enzymatic attack on immobilized substrates. 2. Diffusional limitations in the alpha-chymotrypsin-catalyzed hydrolysis of polyacrylamide-bound l-phenylalanine 4-nitroanilide

Detection of human neutrophil elastase with peptide-bound cross-linked ethoxylate acrylate resin analogs

An assessment of elastase-substrate kinetics and adsorption at the solid-liquid interface of peptide-bound resin was made in an approach to the solid-phase detection of human neutrophil elastase (HNE), which is found in high concentration in chronic wound fluid. N-succinyl-alanine-alanine-proline-valine-p-nitroanilide (suc-Ala-Ala-Pro-Val-pNA), a chromogenic HNE substrate, was attached to glycine-cross-linked ethoxylate acrylate resins (Gly-CLEAR) by a carbodiimide reaction. To assess the enzyme-substrate reaction in a two-phase system, the kinetic profile of resin-bound peptide substrate hydrolysis by HNE was obtained. A glycine and di-glycine spacer was placed between the resin polymer and substrate to assess the steric and spatial requirements of resin to substrate with enzyme hydrolysis. The enzymatic activities of suc-Ala-Ala-Pro-Val-pNA and suc-Ala-Ala-Pro-Ala-pNA on the solid-phase resin were compared with similar analogs in solution. An increase in visible wavelength absorbance was observed with increasing amounts of substrate-resin and enzyme concentration. Enzyme hydrolysis of the resin-bound substrate was also demonstrated on a polypropylene surface, which was employed for visible absorbance of released chromophore. A soluble active substrate analog was released from the resin through saponification of the ethoxylate ester linkages in the resin polymer. The resin-released conjugate of the HNE substrate demonstrated an increased dose response with increasing enzyme concentration. The synthesis and assay of elastase substrates bound to CLEAR resin gives an understanding of substrate-elastase adsorption and activity at the resin's solid-liquid interface for HNE detection with a solid-phase peptide.

Specificity of chymosin on immobilized bovine B-chain insulin

1. The specificity of chymosin on immobilized bovine B-chain insulin is studied. 2. Eight sites of hydrolysis are determined.

Dextran-linked purine nucleosides as substrates and inhibitors of adenosine deaminase

Dextran-bound adenosine, inosine, and nebularine have been prepared by carbodiimide coupling of their 2',3'-O-(4-carboxyethyl-1-methylbutylidene) cyclic acetal derivatives to 6-aminohexyldextran or 12-aminododecanyldextran. The latter polymers were prepared by cyanogen-bromide activation of dextran T80 followed by reaction with 1,6-diaminohexane or 1,12-diaminododecane. A high CNBr concentration leads to high-molecular-weight material, probably due to cross-linking, accompanied by a decrease in the digestion velocity using endo-dextranase from Penicillium species (EC 3.2.1.11). The dextran-bound nucleosides, as well as the nucleoside 2',3'-O-(4-ethoxycarbonyl-1-methylbutylidene) acetal derivatives, were tested as substrates and inhibitors for adenosine deaminase. The Km of the adenosine acetal ester is identical to that of adenosine which shows that acetalation does not hinder complex formation. Since the maximum velocity of deamination is decreased fourfold, the modified substrate does not fit as well as the nucleoside. The polymer-bound acetals show a 3-8-fold increase of Km or Ki and unchanged V compared to the corresponding acetals while dextranase digestion of the support does not alter the kinetic data. This indicates that the length of the polysaccharide chain does not interfere either with the complex formation or with the catalytic activity of the modified substrate. Since the activation energies of the deamination reactions of adenosine, its acetal ester, and dextran-linked adenosine are all similar (29.8-32.3 kJ mol-1) it is concluded that no diffusion control of the enzymatic reaction results from the binding of the nucleoside acetals to dextran T80.