杀虫剂及不同地区寄主植物对棉蚜酯酶的影响

通过滤纸酯酶反应法比较 4种有机磷杀虫剂对北京和山东高密地区取食不同寄主植物的棉蚜β-乙酸萘酯 (β -NA)酯酶的抑制作用。结果表明高密地区不同寄主植物上的棉蚜 β -NA酯酶活力高的个体多于北京地区 ,同时辛硫磷对高密地区不同寄主植物上的棉蚜 β -NA酯酶的抑制作用亦高于北京地区 ,而久效磷和DDVP对两地区不同寄主植物上的棉蚜种群中 β-NA酯酶的抑制作用相似。     

Extracellular lipolytic activity in Phoma glomerata

Several properties of the lipolytic activity exhibited by the conidial fungus Phoma glomerata were studied. Lipolytic activity in an aqueous buffer medium was measured on triacylglycerol, phosphoglyceride and cholesterol ester under different experimental conditions. The effect of storage temperature on the stability of the hydrolytic activity, and optimal conditions of temperature and time of maximal activity were determined. The optimal conditions for maximal lipolytic activity were found to be 40–50 °C and 1 h. The activity released to the medium by 1 mg cells for 1 h at 40 °C was stated as the enzyme released unit (ERU). The protein fraction of MW > 50 kDa obtained by ultrafiltration of the medium, was active on the three substrates assayed, and it showed a non-specific hydrolytic activity on both the 1- and 2-acyl esters either in the neutral glyceride or in the phosphoglyceride. A protein of M _r approx. 75 kDa was the only one that showed esterase activity. The crude medium, stored at –15 °C, maintained its initial hydrolytic activity on triacylglycerol for at least 42 days, though when it was kept for 10 days at 4 °C, the activity fell to 50%. Kinetic parameters using substrates such as triolein (TO), dipalmitoyl phosphatidylcholine (DPPC) and cholesteryl oleate (ChoO), were comparatively evaluated. The activity of the enzyme in the hydrolysis of TO showed the highest values, whereas the maximal specific activities were less when the enzyme was assayed against DPPC and ChoO.     

节节麦的酯酶同工酶分析

对 30份不同来源的节节麦进行 4个时期的酯酶同工酶分析。结果表明 :不同来源节节麦的酯酶同工酶存在较大差异 ,共分成 1 5种基本类型。我国黄河流域的 1 0份节节麦被划分为 2个基本类型 ,但二者关系极为相近 ;新疆节节麦与之有一定差异 ,但在相似系数≤ 0 .82 0时可视为一类。所有材料在 4个时期之间没有出现一个完全相同的酶带类型 ,说明酯酶同工酶随发育时期而不断变化。     

A method for studying histochemical reactions in intact human dentine with a polarizing incident light microscope

Localization and distribution of non-specific esterases has been studied in intact human dentine, by reflected light microscopy. The method of specimen preparation described here permits the visualization of optical sections in depth within the specimen at high optical resolution. Non-specific esterase was found deposited as discrete bands across the tubules. or as droplets, or as a diffuse microsomal variety in the dentinal tubules and in the interglobular spaces. It was possible to distinguish the droplet variety from the microsomal variety, of esterase within the same tubule, by means of a novel optical method using antiflex and differential interference contrast systems of reflected light microscopy. It was found that the coefficient of reflection of dentine diminished gradually from the enamel to the pre-dentine and was inversely related to the scattering of light in dentine. This scattering plays an important role in the formation of the image with reflected light microscopy. The reflected light microscope offers an economically attractive alternative or a supplementary mode of microscopy to the confocal scanning microscopes for studying intact dentine at varying depths.     

Isoenzymes of naphthyl acetate esterase in senescing leaves of Festuca pratensis

Naphthyl acetate esterase (NAE) of leaves of Festuca pratensis had an apparent MW of 55000. Five major NAE isoenzymes were resolved by gel electrophoresis. During leaf senescence the proportions of these isoenzymes altered and two novel isoenzymes became active. Cycloheximide applied to leaves delayed and diminished the responses of NAE isoenzymes during senescence. The two novel NAEs were similar in MW and substrate affinity to pre-existing NAEs. Partially-purified NAE had no cholinesterase, carboxypeptidase, ethyl acetate esterase or ethyl butyrate esterase activity. Lack of inhibition by eserine, PCMB and organophosphorus insecticide classified these enzymes as acetylesterases.     

Transacetylation of carbohydrates in organic solvent catalysed by O-acetylpeptidoglycan esterase from Neisseria gonorrhoeae

The potential of the Neisseria gonorrhoeae O-acetylpeptidoglycan esterase (Ape1a) for catalysing transacetylations in organic solvents with a number of carbohydrate acceptors was investigated. The performance of the enzyme was observed to improve as the polarity index of the solvent increased. The best transacetylation conditions were determined to be a 1:6 phosphate buffer/ethyl acetate system, where Ape1a catalysed approximately 28% acetylation of 4-methylumbelliferyl-N-acetylglucosamine using p-nitrophenyl acetate as donor. Further analysis of the acetylated products by reverse phase HPLC and ESI-mass spectrometry confirmed the presence of monoacetylated 4-methylumbelliferyl-N-acetylglucosamine. Under identical reaction conditions, the enzyme also performed transacetylations using ethyl acetate or vinyl acetate as donor. These results demonstrated the feasibility of using the bacterial cell wall enzyme Ape1a to generate hitherto unattainable compounds which may be used as antagonists of peptidoglycan-metabolizing enzymes.     

Some differences in intracellular distribution and properties of the chymotrypsin-like esterase activity of human and rabbit neutrophils

The intracellular localization and properties of the chymotrypsin-like esterase activity ($\text{N-}\text{acetyl}\text{-}\text{DL}\text{-}\text{phenlylalanine}\text{β-}\text{naphthyl}$ esterase acitivity) of the rabbit peritoneal neutrophil has been studied and shown to differ from that of the human neutrophil.The major portion of the esterase activity in the rabbit neutrophil is in the 100 000 × g supernatant fraction with distinctly less activity in the lysosomal fraction. The 100 000 × g supernatant contained the highest relative specific activity of any of the subcellular fractions. Rabbit peripheral blood neutrophils gave the same distribution.The 100 000 × g supernatant esterase is 95% esterase 1 and 5% esterase 3, whereas, the lysosomal esterase is 78% esterase 1, 10–16% esterase 2 and 9% esterase 3 as defined by their ability to be inhibited by p-nitrophenyllethyl-5-chloropentylphosphonate. The 100 000 × g supernatant The 100 000 × g supernatant and lysosomal esterase activities further differ in their susceptibility to other inhibitors, their pH optima, ease of elution from DEAE and isoelectric points. Two molecular weight species of 174 000 and 70 000 were found in the 100 000 × g supernatant fraction and extracts of the lysosomal fraction but usually in differing proportions.In confirmation of others, essentially all of the chymotrypsin-like esterase activity ($\text{N-}\text{acetyl}\text{-}\text{DL}\text{-}\text{phenlylalanine}\text{β-}\text{naphthyl}$ esterase activity) of the human neutrophil is in the lysosomal fraction, unlike the rabbit cell. The human neutrophil esterase was less susceptible to inhibition by p-nitrophenylethyl-5-chloropentylphosphonate and diisopropylphosphofluoridate but more susceptible to soybean trypsin inhibitor than rabbit esterase activity. The pH optimum of the human neutrophil esterase differed from either the rabbit lysosomal or 100 000 × g supernatant esterase, as did the isoelectric point and molecular weights.     

Optimizing Immobilization and Stabilization of Feruloyl Esterase from Humicola Insolens and its Application for the Feruloylation of Oligosaccharides

Feruloyl esterase (FAE)-catalyzed esterification reaction is as a potential route for the biosynthesis of feruloylated oligosaccharides as functional ingredients. Immobilization of FAE from Humicola insolens on metal chelate-epoxy supports was investigated. The study of effects of immobilization parameters using response surface methodology revealed the significance of enzyme/support ratio (3.25-29.25 mg/g support), immobilization time (14-38 h), buffer molarity (0.27-1.25 M) and pH (4.0-8.0). The interactions between enzyme-to-support ratio/buffer molarity and enzyme-to-support ratio/pH were found to be critical for the modulation of the immobilization activity yield and the retention of specific activity, respectively. Optimum conditions for FAE-immobilization on metal chelate Sepabeads® EC-EP R were identified to be 22.75 mg FAE/g support, pH of 5.0, 27.7 h and buffer molarity of 0.86 M. At these conditions, an activity yield of 82.4%, a specific activity retention of 143.4%, and an enzyme activity of 395.4 μmol/min. g support were achieved. Further incubation of the immobilized FAE at pH 10.0 improved its thermostability. Increasing the pore size of the epoxy support improved the retention of FAE hydrolytic activity and the esterifying efficiency of the immobilized biocatalyst. Optimally immobilized and stabilized FAE on metal chelate-epoxy support retained up to 92.9% of the free enzyme feruloylation efficiency to xylooligosaccharides..     

Regioselective Enzymatic Hydrolysis of 3',5'-DI-O-Acetylthymidine and Observation of a Surface Effect Due to Polystyrene

The selective enzymatic hydrolysis of 3',5'-di-O-acetylthyidine (1) was studied. The lipases from porcine pancreas and Aspergillus niger, and pig liver esterase, all catalysed selective hydrolysis of the 5'O-acetyl group, but the lipase from Candida cylindracea catalysed selective hydrolysis of the 3'-O-acetyl group. Highest selectivity, leading to essentially pure 3'-O-acetylthymidine, was achieved using porcine pancreatic lipase in dilute solution at pH 7.5. Provision of an artificial interface in the form of polystyrene beads led to a significant increase in the rate of hydrolysis, accompanied by a marked fall in selectivity. Other changes in the hydrolysis conditions, such as raising the concentration of substrate or adding cosolvent, also led to a fall in selectivity.