Biomedical subjects

I Ohsawa

Publications and source records attributed to I Ohsawa.

57 records · Page 4Linked to original sources

PubMed1988

Effects of phospholipids on hydrolysis of trioleoylglycerol by human serum carboxylesterase.

Human serum carboxylesterase (EC 3.1.1.1), purified by affinity chromatography on trimethylammonium anilinium-Sepharose, hydrolyzed the short-chain fatty acid ester tributyrin (40 mumol/mg protein per h), but scarcely hydrolyzed the long-chain fatty acid ester triolein (less than 0.2 mumol/mg protein per h). Phospholipids enhanced triolein hydrolysis by carboxylesterase to various extents, cardiolipin causing the most enhancement (2.5 mumol/mg protein per h). Phosphatidylserine and phosphatidylinositol also enhanced carboxylesterase-catalyzed hydrolysis of triolein (450-980 nmol/mg protein per h). The optimal pH for tributyrin hydrolysis was pH 8.0, but the pH range for triolein hydrolysis was broad, being pH 4.5-7.5. The rates of hydrolyses of monoolein, diolein and triolein by carboxylesterase in the absence and presence of 100 micrograms/ml cardiolipin were 3.9, 0.5 and 0.2 mumol/mg esterase per h and 2.0, 0.6 and 4.0 mumol/mg protein per h, respectively. Thus, on addition of cardiolipin, triolein hydrolysis was enhanced, but tributyrin hydrolysis was reciprocally decreased. Triton X-100 (0.1%) and NaCl (1.0 M) decreased triolein hydrolysis, but did not decrease tributyrin hydrolysis. Mercaptoethanol decreased triolein hydrolysis, but not tributyrin hydrolysis. These results suggest that cardiolipin modifies the interaction of carboxylesterase with substrates in such a way as to facilitate its interaction with a hydrophobic substrate, and that disulfide bonding might be involved in the substrate recognition site.

Carboxylesterase↗

PubMed1985

Human plasma carboxyl esterase-catalyzed triolein hydrolysis. Existence of promoting factor in serum.

The possibility that some factor in serum changes the substrate specificity of purified human plasma carboxyl esterase, which hydrolyzes the short chain fatty acid ester, tributyrin, was investigated. The purified carboxyl esterase from human plasma hydrolyzed 48 mmol of tributyrin/mg of protein/h, monoolein at 1560 mumol of released fatty acids/mg of protein/h, diolein at 133 mumol of released fatty acids/mg of protein/h, and triolein at less than 10 mumol of released fatty acids/mg of protein/h. When human serum was applied to phenyl-Sepharose, a triolein hydrolysis-promoting factor (THPF) for purified carboxyl esterase was bound to the gel and was eluted with water. This partially purified human serum THPF enhanced carboxyl esterase-catalyzed triolein hydrolysis about 30-fold, diolein hydrolysis 2-fold, and monoolein hydrolysis 1.5-fold. Hydrolysis of triolein in very low density lipoproteins (d less than 1.006) and intermediate lipoproteins (1.006 less than d less than 1.019) by carboxyl esterase was also enhanced by addition of THPF. THPF activity was reduced by treatment of delipidation, but resistant to trypsin treatment or heating at 50 degrees C. These results indicated that serum carboxyl esterase can hydrolyze the long chain fatty acid ester, triolein, in the presence of triolein hydrolysis-promoting factor in serum.

Carboxylic Ester Hydrolases↗

PubMedDate not supplied

Effects of glimepiride on in vivo insulin action in normal and diabetic rats.

To evaluate the effects of glimepiride on insulin action in peripheral tissues, we investigated insulin-induced glucose uptake in normal and diabetic rats using the euglycemic clamp procedure (insulin infusion rates: 6 and 30 mU/kg/min). Normal rats: After oral administration of glimepiride (0.1 mg/kg/day; NG) or saline (NC) for 2 weeks, euglycemic clamp procedures were performed. During submaximal hyperinsulinemia (620 +/- 35 pmol/l, mean +/- S.E.M.), metabolic clearance rates of glucose (MCR) in NG were significantly higher than in NC (25.1 +/- 2.1 vs. 18.3 +/- 1.2 ml/kg/min, P < 0.05). During maximal hyperinsulinemia (5235 +/- 270 pmol/l), MCRs in NG were higher than in NC, but there was no statistical significance (43.3 +/- 2.8 and 38.9 +/- 2.8). Diabetic rats: streptozotocin-induced diabetic rats were divided into four groups, GI (glimepiride treatment, 0.1 mg/kg/day p.o., with insulin, 5 U/day s.c.), SI (insulin alone), SG (glimepiride alone), and SC (saline). MCRs in the four groups were similar during 6 mU/kg/min clamps. During 30 mU/kg/min clamps, MCRs in GI were significantly higher than those in SC, SG or SI (23.4 +/- 2.8 vs. 12.2 +/- 1.9 and 8.9 +/- 0.8, P < 0.01, and vs. 17.4 +/- 1.5, P < 0.05). Although MCRs in SI tended to be higher than in SC, there was no significant statistical difference between these two groups. These results suggest that glimepiride enhances insulin action in peripheral tissues, and that glimepiride treatment with insulin improves the insulin resistance observed in streptozotocin-induced diabetic rats.

Administration, Oral↗