Title: Efficient monoacylglycerol synthesis by carboxylesterase EstGtA2 from Geobacillus thermodenitrificans in a solvent-free two-phase system Osamura T, Nonaka K, Takahashi F, Okuda M, Hagihara H, Takimura Y Ref: J Biosci Bioeng, :, 2022 : PubMed
The present study investigated high-yield monoacylglycerol (MAG) synthesis by bacterial lipolytic enzymes in a solvent-free two-phase system. Esterification by monoacylglycerol lipase from Bacillus sp. H-257 (H257) required a high glycerol/fatty acid molar ratio for efficient MAG synthesis. Screening of H257 homologues revealed that carboxylesterase derived from Geobacillus thermodenitrificans, EstGtA2, exhibited a higher esterification rate than H257. Moreover, neutralizing the pH of the acidic reaction solution by adding potassium hydroxide (KOH) solution further increased the esterification rate. The esterification rate by EstGtA2 reached 75% under conditions of equivalent molar amounts of glycerol and fatty acid, and the MAG rate (MAG/total glyceride) was 97%. The neutralized pH of the reaction solution likely affected the thermal stability of EstGtA2 during the esterification reaction. Screening for thermal-tolerant variants revealed that the EstGtA2(S26I) variant was stable at 75 degreesC for 30 min, a condition under which wild-type EstGtA2 was completely inactivated. The esterification rate by the EstGtA2(S26I) variant reached 90%, and the MAG rate was 96%. The addition of alkali and the use of a thermal-tolerant enzyme were important for obtaining high-yield MAG in a solvent-free two-phase system utilizing EstGtA2.
Title: Contribution of Human Liver and Intestinal Carboxylesterases to the Hydrolysis of Selexipag In Vitro Imai S, Ichikawa T, Sugiyama C, Nonaka K, Yamada T Ref: J Pharm Sci, 108:1027, 2019 : PubMed
In liver microsomes, selexipag (NS-304; ACT-293987) mainly undergoes hydrolytic removal of the sulfonamide moiety by carboxylesterase 1 (CES1) to yield the pharmacologically active metabolite MRE-269 (ACT-333679). However, it is not known how much CES in the liver and intestine contributes to the hydrolysis of selexipag or how selexipag is metabolized in the intestine, including by hydrolysis. To obtain a better understanding of selexipag metabolism in humans, we determined the percentage contribution of CES1 and carboxylesterase 2 (CES2) to the hydrolysis of selexipag and 7 of its analogs with different sulfonamide moieties and evaluated its nonhydrolytic metabolism in human liver microsomes and human intestinal microsomes (HIMS). For selexipag, the percentage contributions of CES1 and CES2 in human liver microsomes were 77.0% and 9.99%, respectively, while the percentage contribution of CES2 in HIMS was 100%. In HIMS, the rate of hydrolysis of selexipag was the lowest among the compounds tested, and no difference between the presence and absence of nicotinamide adenine dinucleotide phosphate was noted. We infer from these results that selexipag is likely to be hydrolyzed by CES2 as well as CES1, and only selexipag itself and the MRE-269 produced by hydrolysis in the intestine would be absorbed after oral administration.
Muraminomicin is a lipopeptidyl nucleoside antibiotic produced by Streptosporangium amethystogenes SANK 60709. Similar to several members of this antibiotic family such as A-90289 and muraymycin, the structure of muraminomicin consists of a disaccharide comprised of two modified ribofuranose units linked by an O-beta(1 --> 5) glycosidic bond; however, muraminomicin holds the distinction in that both ribose units are 2-deoxy sugars. The biosynthetic gene cluster of muraminomicin has been identified, cloned and sequenced, and bioinformatic analysis revealed a minimum of 24 open reading frames putatively involved in the biosynthesis, resistance, and regulation of muraminomicin. Fives enzymes are likely involved in the assembly and attachment of the 2,5-dideoxy-5-aminoribose saccharide unit, and two are now functionally assigned and characterized: Mra20, a 5'-amino-2',5'-dideoxyuridine phosphorylase and Mra23, a UTP:5-amino-2,5-dideoxy-alpha-D-ribose-1-phosphate uridylyltransferase. The cumulative results are consistent with the incorporation of the ribosyl appendage of muraminomicin via the archetypical sugar biosynthetic pathway that parallels A-90289 biosynthesis, and the specificity for this appendage is dictated primarily by the two characterized enzymes.
Sitagliptin is an oral, potent, highly selective, once-daily DPP-4 inhibitor indicated for the treatment of type 2 diabetes mellitus (T2DM). To assess the dose-ranging efficacy and safety/tolerability profile of once-daily sitagliptin 25, 50, 100, and 200 mg in Japanese patients with T2DM. In this randomized, double-blind, placebo-controlled study, 363 Japanese patients with inadequate glycemic control (HbA(1c)=6.5-10%; FPG< or =270 mg/dL) were randomized (1:1:1:1:1) to placebo, sitagliptin 25, 50, 100, or 200 mg q.d. for 12 weeks. The primary endpoint was change from baseline in HbA(1c) at Week 12. At Week 12, treatment with sitagliptin at all doses tested provided significant (p<0.001) reductions in HbA(1c) (-0.69 to -1.04%) from baseline (7.49 to 7.65%) relative to placebo. Sitagliptin significantly (p<0.001) reduced fasting plasma glucose (FPG; -15.9 to -23.2 mg/dL) and 2-hour postprandial glucose (2-hr PPG; -40.3 to -65.0 mg/dL) relative to placebo, in a dose-dependent manner. At doses > or =50 mg, differences in HbA(1c), FPG, and 2-hr PPG between the sitagliptin groups were not statistically significant. Sitagliptin was generally well tolerated with a low and similar incidence of hypoglycemia and minimal weight gain relative to placebo. Treatment with sitagliptin for 12 weeks provided significant and clinically meaningful reductions in HbA(1c), FPG, and 2-hr PPG across the dose range studied and was generally well tolerated in Japanese patients with T2DM.
AIM: To evaluate the significance of the expression of vascular endothelial growth factor (VEGF), its correlation with clinicopathological variables were studied in the tissue of hepatocellular carcinoma (HCC) and surrounding liver. METHODS: In 56 samples (tumor and non-tumor liver tissue) collected from 28 patients, VEGF expression was examined by immunohistochemistry and western blot analysis. RESULTS: The value of VEGF expression by western blotting was correlated with immunohistochemical staining grade. In tumor tissue, the value of VEGF expression correlated with tumor size (P = 0.034), a-fetoprotein (P = 0.036) and protein induced by vitamin K absence-II by simple regression, and histological grade (P = 0.0132) by the unpaired t-test. The level of VEGF expression in non-tumor liver was found to correlate with the value of serum albumin (P = 0.008), cholinesterase (P = 0.012) and prothrombin activity (P = 0.046). The frequency of simple nodular type in gross appearance decreased in cases with high tumor/non-tumor (T/N) ratio (P = 0.022), and the degree of portal vein invasion progressed with an increase in the T/N ratio (P = 0.008). The T/N ratio was significantly higher in early recurrence cases (P = 0.0081). CONCLUSION: This study on the expression of VEGF might be useful to estimate the liver condition and the clinicopathological features of HCC.
The biosynthetic gene cluster for the enediyne antitumor antibiotic neocarzinostatin (NCS) was localized to 130 kb continuous DNA from Streptomyces carzinostaticus ATCC15944 and confirmed by gene inactivation. DNA sequence analysis of 92 kb of the cloned region revealed 68 open reading frames (ORFs), 47 of which were determined to constitute the NCS cluster. Sequence analysis of the genes within the NCS cluster suggested dNDP-D-mannose as a precursor for the deoxy aminosugar, revealed two distinct type I polyketide synthases (PKSs), and supported a convergent model for NCS chromophore biosynthesis from the deoxy aminosugar, naphthoic acid, and enediyne core building blocks. These findings shed light into deoxysugar biosynthesis, further support the iterative type I PKS paradigm for enediyne core biosynthesis, and unveil a mechanism for microbial polycyclic aromatic polyketide biosynthesis by an iterative type I PKS.
