Genichiro Oshima

Peptide inhibitors of angiotensin I-converting enzyme in digests of gelatin by bacterial collagenase.

Peptide inhibitors of angiotensin I-converting enzyme (peptidyldipeptide hydrolase, EC 3.4.15.1) were produced by digesting gelatin with bacterial collagenase. The inhibitors were isolated from the digests with a combination of alcohol fractionation, treatment with Amberlite CG-50 column, gel filtration through Sephadex G-25, and Dowex 50 column and paper chromatography. Nine peptide fractions were purified to apparent homogeneity judging by thin-layer and ion-exchange column chromatography, and amino acid composition. Amino acid sequences of the peptides were determined: 2 were found to be mixtures of peptides and the sequence of another was only partially determined. Six of the peptides were potent inhibitors of the converting enzyme, while the other three were less active. 6 peptides were substrates for the enzyme. The enzyme released a dipeptide, Ala-Hyp from one peptide and was strongly inhibited by this dipeptide. The remainder of the parent peptides was a less effective inhibitor.

pH dependence of salt activation of human leukocyte elastase

The effects of pH on salt stimulation of the rates of hydrolysis of three substrates by human leukocyte elastase were studied. The enzyme was most active at pH 10.5, 8.0-8.5, and 9.5 for the hydrolyses of fluorescein isothiocyanate-labeled S-carboxymethylated bovine serum albumin (FITC-CM-BSA), succinyl-L-Ala-L-Pro-L-Ala-7-methylcoumaryl-4-amide (Suc-APA-MCA), and succinyl-L-Ala3-p-nitroanilide (Suc-Ala3-pNA), respectively, in the absence of NaCl. The enzyme was activated by 0.5 M NaCl similarly at all pHs tested for the hydrolysis of Suc-Ala3-pNA, but more at neutral and alkaline pH values, respectively, for the hydrolyses of FITC-CM-BSA and Suc-APA-MCA. Thus, in the presence of 0.5 M NaCl, the enzyme was most active at pH 8.0 and 10.0 with FITC-CM-BSA and Suc-APA-MCA, respectively. In contrast, the proteolytic activity of porcine pancreatic elastase was somewhat inhibited by 0.5 M NaCl.

Abolition by dextran sulfate of the heparin-accelerated antithrombin III/thrombin reaction

Dextran sulfate did not inhibit the amidolytic activity of thrombin on Boc-Val-Pro-Arg-4-methylcoumaryl-7-amide, but abolished inhibition of the enzyme with antithrombin III (AT III) in the presence of heparin. Dextran sulfate did not bind to AT III and had less affinity than immobilized heparin for the protein. Dextran sulfate bound strongly to thrombin and had higher affinity than immobilized heparin for the enzyme. These findings indicate that binding of dextran sulfate to a site other than the active site of thrombin to prevent the approach of AT III in the presence of heparin.

Solid surface-catalysed inactivation of bovine α-chymotrypsin in dilute solution

Abstract Although loss of chymotrypsin activity in dilute solution deviated from first order kinetics at low enzyme concentration, it displayed first order kinetics at concentrations more than 4 nM. First order rate constants varied with the ratio of surface area to volume, with the kind of vessel containing the enzyme, and with the particular test material (DS, polybrene, lecithin or BSA) coating the vessel. The reaction was saturable at lower chymotrypsin concentrations in glass than in polypropylene tubes, while less enzyme was lost at high concentrations. All these facts showed that loss of enzyme activity is incompletely, but markedly, due to a solid surface-catalysed reaction. Intrinsic fluorescence of native chymotrypsin at pH values 8 and 3, and of active site-blocked enzyme, decreased with time at 37°C. No extensive autolysis of chymotrypsin was observed during the time-dependent loss of enzyme activity. Therefore, the apparent loss of chymotrypsin activity in dilute solution was mainly due to an irreversible conformational change of the molecules, as associated with the solid-surface-catalysed reaction.

Trigger action of dextran sulfate on inactivation of thrombin

Inactivation of thrombin was enhanced by dextran sulfate (DS) coated on polypropylene tubes with plastic adhesive. Long interaction of thrombin with DS was not essential to enhance the enzyme inactivation. Albumin inhibited the inactivation of thrombin by DS-coated tubes, but had no effect after interaction of the enzyme with DS. NaCl, especially, sodium ions, inhibited the inactivation by DS-coated tubes. Enzyme inactivation occurred at 37 degrees C, but not at 4 degrees C. Thus, the inactivation was due not only to ionic interaction with DS, but also to intramolecular perturbation of thrombin.

Stimulation by dextran sulfate of denaturation of bovine thrombin

At high thrombin concentration, loss of enzyme activity was proportional to the initial enzyme concentration. At low thrombin concentration, loss of activity followed first order kinetics, indicating mainly denaturation (inactivation) of the enzyme. Dextran sulfate stimulated thrombin denaturation, while serum albumin and polyethylene glycol 6000 (PEG) protected the enzyme from denaturation. These results indicate that the enzyme molecule is stabilized by weak interactions with albumin and PEG, but destabilized by strong interaction with dextran sulfate.

Effect of NaC1 on inactivation of bovine thrombin by antithrombin III in the presence of low affinity-heparin or dextran sulfate

Heparin with low affinity (LA-heparin) to antithrombin III (AT III) enhanced the rate of inactivation of thrombin by AT III. The enhancement of the rate was saturable with AT III and was proportional to the LA-heparin concentration. Although the rate-enhancement in the presence of LA-heparin decreased with increase in NaC1 concentration, it was comparable with that in the presence of high affinity-heparin (HA-heparin) in the absence of NaC1. Inactivation of thrombin by AT III in the presence of dextran sulfate (DS) was also sensitive to NaC1 concentration. These findings indicate that free AT III is favorable for binding to the complexes of thrombin and highly sulfated polysaccharides having low affinities to AT III in the absence of NaC1.

Stimulation by polysulphates of inactivation of trypsin and plasmin

Abstract Three polysulphates [heparin, dextran sulphate (DS) and polyvinyl sulphate (PVS)] stimulated inactivation of trypsin in the absence of NaCl, but only PVS stimulated it in 0.1 m NaCl. The inactivation of trypsin depended on time and temperature and was not restored by adding NaCl. Stimulation by heparin of the trypsin inactivation was slightly protected by albumin. Long interaction of trypsin with DS was not essential to stimulate the enzyme inactivation. The intrinsic fluorescence of trypsin changed instantaneously by adding DS in the absence of NaCl, and it decreased more rapidly than the native enzyme. All these results indicate that trypsin molecules interacted once with the polysulphates are more labile and inactivated rapidly and irreversibly than the native molecules. Inactivation of plasmin was also stimulated by these polysulphates in the presence of 0.1 m NaCl, indicating that their interactions were stronger than the polysulphate-trypsin interaction.

Effects of different ions on the interactions of heparin with bovine antithrombin III and thrombin

Of four Tris-salts tested (chloride, sulfate, phosphate and acetate), chloride caused complete elution of antithrombin III (AT III) from a heparin-Sepharose column and sulfate caused partial elution. AT III was also partially eluted from the column with sodium acetate, but not Tris acetate. On the other hand, thrombin was eluted from the column with the Tris-salts in the order chloride greater than sulfate greater than acetate, but was not eluted with Tris-phosphate. Thrombin was also eluted from the column with sodium acetate. These findings indicate that the affinity of heparin to AT III was influenced only by strongly electronegative ions, whereas its affinity to thrombin was affected by both strongly electropositive and strongly electronegative ions.

Mode of action of bacterial collagenase on a synthetic substrate, (Pro-Pro-Gly)5

Clostridial collagenase (EC 3.4.24.3) catalyzes the hydrolysis of (Pro-Pro-Gly)5 at minimum of three different rates, producing Pro-Pro, Gly-Pro-Pro and Gly-Pro-Pro-Gly, and various intermediate peptides. The intermediate and final products were separated by cation-exchange column chromatogrphy and identified, and their rates of formation were measured. Pro-Pro was released most rapidly with formation of the tridecapeptide. After the initial release of the N-terminal Pro-Pro, hexa- and heptapeptides were formed in larger amounts than tri-, tetra-, nona- and decapeptides from the tridecapeptide. The rates of disappearance of the intermediates decreased in the order trideca- greater than deca- and nona- greater than heptapeptide. The results indicate that the enzyme hydrolyzes inner linkages of the tridecapeptide having N- and C-terminal Gly residues, forming large peptides, preferentially to outer linkages, forming the tri- and tetrapeptides.