Chemical modification of enzymes with activated magnetic modifier

An activated magnetic modifier, which could render biological materials magnetic property, was synthesized in following two steps: oxidation of ferrous ions (Fe2+) with hydrogen peroxide in the presence of alpha, omega-dicarboxymethylpoly(oxyethylene) (DCPEG) to obtain DCPEG-magnetite (Fe3O4); free carboxyl groups in the DCPEG-magnetite were activated with N-hydroxysuccinimide. By coupling the activated magnetic modifier to amino groups of lipase or L-asparaginase, magnetic enzymes were prepared. They dispersed stably not only in aqueous solution but also in organic solvents with high enzymic activities. Magnetic enzymes were readily recovered from reaction mixture in a magnetic field of 6000 Oe without loss of enzymic activity.

Cooperativity between platelet-activating factor and collagen in platelet aggregation

Cell lysate obtained from cultured vascular endothelial cells contained a substance which induced platelet aggregation. This substance was identified as a phospholipid, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (platelet-activating factor; PAF), by thin-layer chromatography, phospholipase A2 digestion, inhibition by a specific antagonist, CV-3988, and agonist-specific refractory state. It was further found that PAF and collagen together induced extensive aggregation of platelets even with the concentrations by which each agonist alone could not induce aggregation of platelets at all.

Purification of atrial natriuretic peptide receptor from bovine lung. Evidence for a disulfide-linked subunit structure

The receptor for atrial natriuretic peptide (ANP) was purified to apparent homogeneity from bovine lung by a combination of detergent extraction, ammonium sulfate precipitation, and affinity chromatography on ANP-Affi-Gel 10. The Mr of the purified receptor is about 140,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. After reduction, the protein migrated as a single band with an Mr near 70,000. NH2-terminal sequence analysis of the purified material revealed only one sequence, indicating that the ANP receptor is composed of two probably identical subunits held together by disulfide bond(s), although it remains possible that one of the subunits is blocked at the NH2 terminus. Antibody was produced to the nonreduced Mr = 140,000 species and shown to interact with detergent-solubilized forms of the lung and kidney ANP receptor.

Analysis of distribution of receptors among platelets by flow cytometry

We have investigated the binding of fluorescein isothiocyanate (FITC)-labeled fibrinogen to platelets using a fluorescence spectrophotometer and a flow cytometer. The amount of fibrinogen bound by stimulation of adenosine diphosphate (ADP) and 5-hydroxytryptamine (5HT) increased in a dose-dependent manner. Stimulation of one agonist was independent of that of another agonist. Fibrinogen could bind to platelets in response to ADP, regardless of whether they were desensitized by 5HT, and vice versa. It was found by flow cytometric analysis that individual platelets responded uniformly to both ADP and 5HT, indicating that individual platelets have receptors for both ADP and 5HT on their surfaces.

An attempt to determine lipid peroxides with polyethylene glycol-modified hemin

Hemin, having two carboxyl groups, was coupled with alpha-(3-aminopropyl)-omega-methoxypoly(oxyethylene) through the acid-amide bond formed with carbodiimide. The modified hemin catalyzed the peroxidase reaction in 1,1,1-trichloroethane using benzoyl peroxide or peroxides in unsaturated fatty acids as the hydrogen acceptor and leuco crystal violet as the hydrogen donor. A basic study on quantitative microanalysis of the lipid peroxides was attempted.

Magnetic lipase active in organic solvents

Magnetic lipase (magnetite particles coated with polyethylene glycol-modified lipase) was prepared in two steps: Lipase was coupled with 2,4-bis(O-methoxypolyethylene glycol)-6-chloro-s-triazine, activated PEG2, to obtain polyethylene glycol-modified lipase, PEG-lipase. The PEG-lipase was added to the solution of ferrous (Fe2+)- and ferric(Fe3+)-ions with the pH value adjusted to 8.0-8.5 to obtain magnetic lipase. The magnetic lipase was dispersed in organic solvents such as benzene and 1,1,1-trichloroethane with the particle size of 120 +/- 60 nm. The colloidal solution was very stable and no aggregation occurred even after 5 days. A high enzymic activity (11.6 mumol/min/mg protein) for lauryl laurate synthesis was observed in 1,1,1-trichloroethane. The magnetic lipase was readily recovered from the organic solvents in a magnetic field of 6000 Oe without loss of the enzymic activity.

Venom from southern copperhead snake (Agkistrodon contortrix contortrix). I. Characterization of a protease that preferentially releases fibrinopeptide B

Using gel permeation chromatography with high performance liquid chromatograph (HPLC), a highly purified preparation of a protease has been obtained from the venom of the southern copperhead snake (Agkistrodon contortrix contortrix). Both gel permeation chromatography with HPLC and sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that it had an apparent Mr of 60,000-64,000. It consisted of a single polypeptide chain. The activity was inhibited by dithiothreitol. It neither induced platelet aggregation nor activated plasma factor XIII. It cleaved fibrinopeptide B at a rate much faster than fibrinopeptide A from fibrinogen. This specificity was steadily lowered when the incubation temperature was elevated from 0 degrees C to 45 degrees C. Fibrinopeptides were released only at neutral pH.

Characterization of polyethylene glycol-modified L-asparaginase from Escherichia coli and its application to therapy of leukemia

For the purpose of clinical application to the therapy of human leukemia and lymphosarcoma, L-asparaginase from Escherichia coli was modified with 2,4-bis(O-methoxypolyethylene glycol)-6-chloro-s-triazine (activated PEG2) by an improved method, which involves a purification step of activated PEG2 by gel filtration. The PEG2-modified asparaginase retained approximately 30% (73 IU/mg of protein) of the enzymic activity of the native enzyme, while it had almost wholly lost the immunoreactivity towards anti-asparaginase antibodies. The modified enzyme retained the characteristics of the native enzyme in terms of the pH- and temperature-dependencies of activity and stability, and the Km value for L-asparagine. Administration of the modified enzyme to a dog with spontaneous lymphosarcoma induced complete remission without any toxic side effects. Seven children with multiple relapses of acute leukemia were treated with a regimen of cycles of methotrexate and native asparaginase. Three of these children developed anaphylactic shock. In contrast to the native enzyme, the successive administration of PEG2-modified asparaginase to those three patients was therapeutically effective without causing any allergic reaction.

Visible fibrinolysis by endothelial cells: effect of vitamins and sterols

We have succeeded in corroborating the enhancing effect of vitamin A, vitamin C, sitosterol and fucosterol on the fibrinolytic activity of endothelial cells. The assay system consisted of an in situ dissolution of a fibrin layer coated onto a culture dish, over which endothelial cells were grown in a culture medium containing 10% serum. The dissolution was enhanced by the addition of these vitamins and phytosterols to the culture medium.

Inhibition of angiotensin converting enzyme by CV-3317, a non-sulfhydryl compound

N-[N-[(S)-1-Ethoxycarbonyl-3-phenylpropyl]-L-alanyl]-N-(indan-2- yl)glycine hydrochloride (CV-3317) and its de-esterified products, CV-3317-COOH and CV-3317-(5-OH)-COOH, inhibited rabbit lung angiotensin converting enzyme (ACE) with the IC50s of 1.2 X 10(-7), 4.0 X 10(-8) and 4.9 X 10(-8) M, respectively, angiotensin I (A-I)-induced vasoconstriction of the rat aorta (IC50: 2.6 X 10(-7), 2.6 X 10(-8) and 5.4 X 10(-8) M, respectively), and A-I-induced pressor response of the rat kidney (IC50: 3.9 X 10(-7), 3.5 X 10(-8) and 2.8 X 10(-8) M, respectively). In these 3 experiments, both de-esterified products were 4 to 14 times more potent than captopril. In rats, CV-3317 (0.0138 to 138 mumol/kg, p.o.) inhibited plasma and lung ACEs, and the effects at a dose of 0.46 mumol/kg lasted more than 8 hr. CV-3317 inhibited the A-I-induced pressor action in rats (0.138 to 13.8 mumol/kg, p.o. or 0.046 to 0.138 mumol/kg i.v.) and dogs (0.46 to 4.6 mumol/kg, p.o.) in a dose-related manner. CV-3317 was more potent and longer acting than captopril in these in vivo ACE inhibitions. CV-3317 augmented bradykinin-induced hypotension (dogs) and contraction of the ileum (guinea pigs) less potently than captopril. In spontaneously hypertensive rats (SHR), CV-3317 (3 mg/kg, p.o.) markedly inhibited plasma and tissue (aorta, kidney, lung and brain) ACEs; and when administered daily for 2 weeks, it inhibited the plasma, aorta, kidney and lung ACEs; in particular, it markedly inhibited the aortic ACE. Captopril (30 mg/kg, p.o.) markedly inhibited tissue ACEs and slightly plasma ACE, but its inhibitory effects on tissue ACEs, except for the aorta, were unclear by repeated dosings and its effect on plasma ACE was rather enhanced. Thus, the inhibition of vascular ACE may be particularly important for the antihypertensive effect of the ACE inhibitors, including CV-3317, in SHR.

Antihypertensive action of a non-sulfhydryl angiotensin converting enzyme inhibitor (CV-3317) in various hypertensive models

The antihypertensive action of N-[N-[(S)-1-ethoxycarbonyl-3-phenyl-propyl]-L-alanyl]-N-(indan-2-yl) glycine hydrochloride (CV-3317), a nonsulfhydryl compound characterized as an angiotensin converting enzyme inhibitor in our previous work, was examined in hypertensive animal models. In 2-kidney, 1 clip hypertensive rats and dogs, CV-3317 (3 and/or 10 mg/kg, p.o.) produced a sustained antihypertensive action of about 15 to 25 mmHg. Daily oral administrations of CV-3317 (1 to 10 mg/kg/day) to spontaneously hypertensive rats (SHR) for 5 weeks produced a sustained antihypertensive action of 20 to 40 mmHg. When CV-3317 (3 mg/kg) was combined with hydrochlorothiazide (10 mg/kg), its antihypertensive action was intensified in potency and duration. CV-3317 (30 mg/kg) induced a slight hypotension (5 to 10 mmHg) in normotensive rats, but had no effect on the blood pressure of 1-kidney, 1 clip hypertensive rats and on that of a low renin type of DOCA/salt hypertensive rat. The antihypertensive activity of CV-3317 was more potent than that of captopril. In pithed SHR, the pressor response induced by an electrical stimulation of the preganglionic sympathetic nerve, but not the pressor response to norepinephrine, was attenuated by both agents (0.3 mg/kg, i.v.). Both agents may exert their antihypertensive action not only primarily by inhibiting the renin-angiotensin system, but also by inhibiting norepinephrine release from the sympathetic nerve terminals indirectly by reducing the formation of vascular angiotensin II.