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PubMed1988

Purification and characterization of a novel thermostable beta-amylase from Clostridium thermosulphurogenes.

An extracellular beta-amylase from Clostridium thermosulphurogenes was purified 811-fold to homogeneity, and its general molecular, physico-chemical and catalytic properties were determined. The native enzyme was a tetramer of 210 kDa composed of a single type subunit; its 20 amino acid N-terminus displayed 45% homology with Bacillus polymyxa beta-amylase. The beta-amylase was enriched in both acidic and hydrophobic amino acids. The pure enzyme displayed an isoelectric point of 5.1 and a pH activity optimum of 5.5. The optimum temperature for beta-amylase activity was 75 degrees C, and enzyme thermostability at 80 degrees C was enhanced by substrate and Ca2+ addition. The beta-amylase hydrolysed amylose to maltose and amylopectin and glycogen to maltose and limit dextrins, and it was inhibited by alpha- and beta-cyclodextrins. The enzyme displayed kcat. and Km values for boiled soluble starch of 400,000 min-1 per mol and 1.68 mg/ml, respectively. The enzyme was antigenically distinct from plant beta-amylases.

Amino Acid Sequence↗
PubMed1991

Rapid smooth muscle cell growth and endogenous prostaglandin system in spontaneously hypertensive rats.

Vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) exhibit rapid cell growth. In this study, to reveal the mechanisms of the quick VSMC growth, we analyzed the alterations in the respective periods of the proliferating cell cycle, and investigated the role of the endogenous prostaglandin system in this rapid cell growth. The VSMC from SHR showed increased [3H]thymidine uptake and shortened doubling time, compared with Wistar-Kyoto rats (WKY). These properties were mainly due to both shortened transition time from G0/G1 to S and shortened G2 duration. There was a difference neither in the DNA-replication rate nor in the mitotic period. Generating capacity for vasodepressor prostaglandins was significantly reduced in the VSMC from SHR, particularly in the G0/G1 period. When the endogenous prostaglandin synthesis was inhibited by 10(-5) mol/L indomethacin, the transition from G0/G1 to S was shortened. This alteration was eliminated by supplementation with OP41483, a stable prostacyclin analog. In contrast, the alteration in the G2 duration was unaffected by indomethacin. These data indicate that the rapid VSMC growth in SHR is mainly due to the shortening of both the G0/G1 and G2 period, and that the impaired prostaglandin system is responsible, at least in part, for the shortened G0/G1 duration.

Animals↗
PubMed1986

Interaction of soybean beta-amylase with glucose.

The interaction of soybean beta-amylase with glucose was investigated by inhibition kinetics studies and spectroscopic measurements. The inhibition type, inhibitor constant (Ki) and dissociation constant (Kd) of beta-amylase-glucose complex were dependent on pH. At pH 8.0, glucose behaved as a competitive inhibitor (Ki = 34 mM). Binding of glucose produced a characteristic difference spectrum and a change of circular dichroism (CD) at pH 8.1. By using difference absorbance at 292 nm and difference ellipticity at 290 nm, Kd values for beta-amylase-glucose complex were determined to be 45 and 46 mM, respectively. In contrast to pH 8.0, glucose behaved as a mixed-type inhibitor (Ki = 320 mM) at pH 5.4. The Kd values obtained from the difference spectrum were increased by lowering the pH from 8. The pH dependence of the Ki and Kd values suggested that one ionizable group of pK = 8.0, which is shifted to 6.9 by the binding of glucose, controls the binding affinity of glucose. The binding of glucose competed with the binding of cyclohexaamylose and maltose at pH 8.0. The modification of SH groups of the enzyme affected the binding of glucose but did not affect the binding of maltose or cyclohexaamylose at pH 8.0. It was concluded from these results that the binding site of glucose is different from that of maltose and cyclohexaamylose. Presumably, glucose may bind to the subsite 1 of soybean beta-amylase.

Amylases↗
PubMed1983

Difference spectroscopic study of the interaction between soybean beta-amylase and substrate or substrate analogues.

1. In order to investigate the interactions between soybean beta-amylase [EC 3.2.1.2] and ligands (maltotriose as substrate, and maltose and alpha- and beta-cyclodextrins as inhibitors for the hydrolysis of maltoheptaose), the difference spectra were measured at 25 degrees C and pH 5.4, in 0.05 M acetate buffer. Each difference spectrum produced by these ligands showed a clear peak at 292-293 nm due to a tryptophan residue. In addition to this peak, the spectra of alpha- and beta-cyclodextrins showed a specific peak at 298-299 nm, and that of maltotriose showed a shoulder at 298 nm. 2. From the concentration dependency of the difference molar extinction delta epsilon, at 292-293 nm or at 298-299 nm, the dissociation constant of the enzyme-ligand complex, Kd, was evaluated for maltotriose, and alpha- and beta-cyclodextrins. For each ligand, the Kd values obtained at these two wavelengths were in good agreement with Michaelis constant, Km, or the inhibitor constant, Ki. The Kd value for maltose obtained from the titration of delta epsilon at 292 nm was also in good agreement with Ki. 3. Maltose produced a hydrophobic change in the environment of the tryptophan residue, while the interactions of maltotriose, and alpha- and beta-cyclodextrins with this enzyme caused an electrostatic change in the vicinity of the tryptophan residue in addition to the hydrophobic change. Since the signal at 298-299 nm was not found in the difference spectrum of maltose, this signal may be due to a tryptophan residue different from that which produces the signal at 292-293 nm. If both the signals are due to the same tryptophan residue, we must conclude that some conformational change is caused in the enzyme active site by the ligand binding.

Amylases↗
PubMed1989

Differential effects of alpha-, beta- and gamma-cyclodextrins on human erythrocytes.

Alpha-, beta- and gamma-cyclodextrins are cyclic hexamers, heptamers, and octamers of glucose, respectively, and thus are hydrophilic; nevertheless, they have the ability to solubilize lipids through the formation of molecular inclusion complexes. The volume of lipophilic space involved in the solubilization process increases with the number of glucose units in the cyclodextrin molecule and, consequently, cyclodextrins were found to have different effects on human erythrocytes: (a) in the induction of shape change from discocyte to spherocyte the potency was observed to be alpha greater than gamma, but with beta-cyclodextrin hemolysis occurred before the change was complete; (b) in the increase of fluorescence intensity of 1-anilinonaphthalene-8-sulfonate in cyclodextrin-pretreated membranes, the observed potency was beta much greater than gamma greater than alpha; (c) in the release of potassium and hemoglobin, the potency was beta greater than alpha greater than gamma. The potencies of cyclodextrin for solubilizing various components of erythrocytes were alpha greater than beta much greater than gamma for phospholipids, beta much greater than gamma greater than alpha for cholesterol and beta much greater than gamma greater than alpha for proteins. The solubilization potencies were derived from concentration/final-effect curves. The above processes occurred without entry of solubilizer into the membrane, since (a) beta-[14C]cyclodextrin did not bind to erythrocytes and (b) cyclodextrins did not enter the cholesterol monolayer. A study of the [3H]cholesterol in erythrocytes indicated that beta-cyclodextrin extracted this lipid from membrane into a new compartment located in the aqueous phase which could equilibrate rapidly with additional erythrocytes. Therefore, the effects of cyclodextrins differ from those of detergents which first incorporate themselves into membranes then extract membrane components into supramolecular micelles.

Cyclodextrins↗
PubMed1992

Preparation of three positional isomers of diglucosyl-cyclomaltohexaose.

Three positional isomers of diglucosyl-cyclomaltohexaose (diglucosyl-cG6) were chemically synthesized via 6(1),6(2)-, 6(1),6(3)-, and 6(1),6(4)-di-O-(TERT-butyldimethylsilyl)-cG6S (1, 2, and 3) prepared regiospecifically. Glucosylation of bis(2,3-di-O-acetyl)tetrakis(2,3,6-tri-O-acetyl)-CG6S obtained from the three regioisomeric compounds 1, 2, and 3 with 2,3,4,6-tetra-O-benzyl-1-O-trichloroacetimidoyl-alpha-D-glucopyran ose, followed by debenzylation and then deacetylation, afforded 6(1),6(2)-, 6(1),6(3)-, and 6(1),6(4)-di-O-(alpha-D-glucopyranosyl)-cG6S (10, 11, and 12) together with configurational isomers. The desired compounds 10, 11, and 12 containing two (1----6)-alpha-linkages were isolated from the mixtures of their configurational isomers by high performance liquid chromatography. The three diglucosyl-cG6S synthesized chemically were used as authentic samples to identify the components in a mixture of diglucosyl-cG6S produced by an enzymatic process.

Carbohydrate Sequence↗
PubMed1995

[Inhibitory effects of prostaglandin E1.alpha-cyclodextrin (PGE1.CD) on dimethylnitrosamine-induced acute liver damage in rats].

The effects of PGE1.CD on dimethylnitrosamine (DMN)-induced acute liver damage with intravascular coagulation in rats were biochemically and histopathologically investigated. PGE1.CD was administered i.v. from 30 min before to 24 hr after DMN-intoxication (pretreatment) and from 30 min after or from 4 hr after to 24 hr after DMN-intoxication (post-treatment). Pretreatment with PGE1.CD (0.2-2 micrograms/kg/min) dose-dependently suppressed the decrease of platelet counts and the elevation of blood biochemical parameters (PT, HPT, GOT, GPT, LDH, LAP, T-Bil) caused by DMN-intoxication. PGE1.CD (0.5 microgram/kg/min and over) significantly suppressed the DMN-induced histopathological changes (occurrence of hemorrhage and necrosis). Post-treatment with PGE1.CD (2 micrograms/kg/min) also suppressed the liver damage. Furthermore, pretreatment with PGE1.CD (2 micrograms/kg/min) not only suppressed the disruption of hepatocytes, but also prevented the damages of sinusoidal endothelial cells and lysosomal membrane, and it reduced the increase of lipid peroxidation. PGE1.CD (1 microgram/kg/min and over) significantly suppressed the decrease of hepatic tissue blood flow caused by DMN-intoxication. These results demonstrate that PGE1.CD has therapeutically efficacy against DMN-induced acute liver damage in rats; Therefore, it will be clinically useful for the treatment of severe hepatitis such as fulminant hepatitis with intravascular coagulation in the sinusoid.

Acute Disease↗
PubMed1993

Enzymatic synthesis of a novel trisaccharide, glucosyl lactoside.

Cyclomaltodextrin glucanotransferase from Bacillus stearothermophilus produced a series of oligosaccharides by the transglycosylation reaction with cyclomaltohexaose as a glycosyl donor and D-lactose as its acceptor. The content of oligosaccharide A as the main transfer product was 22.1% of the total sugar. The content was increased to 34.1% by hydrolysis with glucoamylase. Oligosaccharide A was isolated by column chromatography and crystallized. By chemical and enzymatic analyses, oligosaccharide A was found to be a novel non-reducing trisaccharide; O-beta-D-galactopyranosyl-(1-->4)-O- beta-D-glucopyranosyl alpha-D-glucopyranoside.

Carbohydrate Sequence↗
PubMed1992

Bile acid and sterol solubilization in 2-hydroxypropyl-beta-cyclodextrin.

The use of 2-hydroxypropyl-beta-cyclodextrin has made it possible to prepare stable aqueous solutions of cholesterol, 26-hydroxycholesterol, 7 alpha-hydroxycholesterol, and monohydroxy bile acids such as lithocholic and 3 beta-hydroxy-5-cholenoic acids. These solutions are suitable for cell culture studies and for parenteral administration to animals.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed1989

[Preventive effect of OP-41483-alpha-CD on cyclosporine A-induced renal tubular and arterial damages].

The aim of this study is to test whether a stable analogue prostaglandin I2 (OP-41483-alpha-CD) (OP) is effective to prevent Cyclosporine A (CsA)-induced nephrotoxicity. Male Lewis rats were administrated with CsA (50 or 100 mg/kg/day, per os) and treated with OP (25 micrograms/kg/day, subcutaneously). For the quantitativeness of qualitative changes, percent area of tubular vacuolization and the grade of renal arteriolar changes were evaluated at light microscopic level, then further examined under electron microscopy. CsA trough levels in the whole blood were also analyzed with HPLC and prostaglandin I2 was assayed by radioimmunoassay of its stable degeneration product 6-keto-PGF1-alpha. As a result, 1) ultrastructurally, perinuclear vacuoles in arteriolar media consisted of cellular intervaginated cytoplasmic processes of neighboring cells, suggesting spastic vasoconstriction induced by CsA, 2) survival rate of OP-treated rats were significantly high compared to that of rats with CsA alone, 3) pathologically, tubular and arterial damages were reduced in OP-treated models, 4) pharmacokinetic studies revealed that CsA trough levels were not different from those of CsA-received alone and OP-treated models, and 5) mean blood 6-keto-PGF1-alpha excretion in rats given CsA was higher than in normal rats.

6-Ketoprostaglandin F1 alpha↗
PubMed1989

The effect on the cornea of alpha cyclodextrin vehicle for cyclosporin eye drops.

We tested four different combinations of alpha-CD and CYA: 0.075% and 80 mg/mL alpha-CD, 0.025% CYA and 40 mg/mL alpha-CD, 0.009% CYA and 20 mg/mL alpha-CD, and 0.003% CYA and 10 mg/mL alpha-CD. We found that 0.025% CYA (alpha-CD[40 mg/mL]) resulted in the least corneal toxicity and penetrated in the cornea 5 to 10 times more than did lipophilic vehicle with CYA.

Administration, Topical↗