微生物酶法转化生产L-肉碱的研究进展

L -肉碱作为一种新型的营养强化剂和临床药物 ,广泛应用于医疗、保健、食品等领域。L- 肉碱的生产方法有化学合成、微生物发酵、微生物酶法转化等 ,其中微生物酶法转化被认为是一种最经济且最有前途的方法。就 3种酶法转化 (DL -肉碱衍生物的酶法拆分、巴豆甜菜碱的酶法转化、D- 肉碱的酶法转化 )的微生物产酶菌株、产酶条件和酶法转化的最适条件作一概述。     

紫外分光光度法测定肉碱转化液中巴豆甜菜碱的含量

通过对巴豆甜菜碱和L－肉碱在紫外188－215mm的光吸收的比较,建立了紫外分光光度法测定肉碱转化液中巴豆甜菜碱含量的方法,测定波长205mm,线性范围0－25ug/ml,该方法快速方便 ,重复性好,可用于L－肉碱生产过程中巴豆甜菜碱的跟踪检测。     

L-肉碱的检测方法

Ｌ 肉碱是参与生物体新陈代谢的重要物质,本文简要介绍和比较了检测肉碱的７种主要方法,即生物法、化学法、酶法、荧光法、高压液相色谱法、 Ｎ Ｍ Ｒ和放射酶法,其中以酶法、荧光法和高压液相色谱法较为常用。     

酶法破碎微生物细胞的研究进展

酶法细胞破碎技术不仅能提高胞内产物的提取效率、降低能耗,还能减少化学试剂的用量,更有利于环保。主要介绍酶法破碎细菌、真菌、微藻、原生菌类等微生物细胞的研究进展、工业化情况以及应用展望。     

果糖-1,6-二磷酸的酶法测定

前言 果糖-1,6-二磷酸（简称FDP）在临床上有广泛用途,主要是作为治疗心脏缺血症的辅助药物,其工业化生产引起了人们越来越浓厚的兴趣。因此,无论是生产或者临床应用试验中,FDP的含量分析都十分重要。     

微生物酶法消除黄酒中氨基甲酸乙酯研究进展

氨基甲酸乙酯(Ethyl carbamate,EC)具有致癌性,广泛存在于酒精饮料中。我国的黄酒因EC含量高而带来的食品安全问题越来越受到人们的关注。微生物酶法消除黄酒中的EC具有直接、高效的特性而被深入研究。文中从黄酒中EC的形成机制、酸性脲酶研究现状、氨基甲酸乙酯水解酶研究现状等方面概述了微生物酶法消除黄酒中EC的研究进展及存在的问题。并针对这些问题,提出了寻找新型氨基甲酸乙酯水解酶、Fe~(3+)依赖型双功能酸性脲酶食品级表达与定向进化及双酶并用将尿素和EC一起消除的策略。     

酶法生产L-苯丙氨酸

<正> 一、前言直到几年前,L—苯丙氨酸(L-phe)主要用作输液,一年不过需要100～200吨。但近来作为人工甜味剂天冬甜精(L-苯丙氨酸甲酯和L-天冬氨酸的肽)的合成原料,对它的需求量显著增加,预测到1990年年需要量近8000吨。L-phe过去主要采用两种方法提供:直     

微生物酶法合成L-半胱氨酸和L-胱氨酸

从土壤中分离到一株假单胞菌Pseudomonas sp.TS1138菌株,其胞内含有DL-2-氨基-Δ²-噻唑啉-4-羧酸(DL-2-Amino-Δ²-Thiazoling-4-Carboxylic Acid,缩写为DL-ATC)水解酶,以培养16h的细胞为酶源,可转化DL-ATC合成L-半胱氨酸。该菌株生长及产酶的最佳碳、氮源为葡萄糖和尿素,DL-ATC对酶的产生具有诱导作用。酶促反应后的产物经薄层层析、旋光度法和高效液相色谱鉴定为L-半胱氨酸。     

L-肉碱的生理功能与生物学方法生产

L-肉碱是动物体内与脂肪酸代谢有关的化合物。它的主要功能是做为载体将长链脂肪酸从线粒体膜外运送到膜内促进脂肪酸的β-氧化。当动物因先天性或代谢性疾病引起体内肉碱缺乏时,会使机体乏力和产生许多心血管疾病。目前L-肉碱除以强化营养用于婴儿和体弱多病者外,还做为药物用于降低血脂、减肥和医治心血管疾病,由于其疗效显著正引起人们的极大兴趣与关注,并正通过生物酶和微生物的转化合成方法对其生产进行积极的研究和开发。     

Comparison of melatonin, vitamin E and L-carnitine in the treatment of neuro- and hepatotoxicity induced by thioacetamide

This study was designed to evaluate and compare the effect of melatonin, vitamin E and L-carnitine on brain and liver oxidative stress and liver damage. Oxidative stress and hepatic failure were produced by a single dose of thioacetamide (TAA) (150 mg kg(-1)) in Wistar rats. A dose of either melatonin (3 mg kg(-1)) vitamin E (20 mg kg(-1) ) or L-carnitine (100 mg kg(-1)) was used. Blood samples were taken from the neck vasculature in order to determine ammonium, blood urea nitrogen (BUN) and liver enzymes. Lipid peroxidation products, glutathione (GSH) content and antioxidative enzymes were determined in cerebral and hepatic homogenates. The results showed a decrease in BUN and in the antioxidant enzymes activities and GSH in the brain and liver. Likewise, TAA induced significant enhancement of lipid peroxidation products levels in both liver and brain, as well as in ammonia values. Melatonin, vitamin E and L-carnitine, although melatonin more significantly, decreased the intensity of the changes produced by the administration of TAA alone. Furthermore melatonin combined with TAA, decreased the ammonia levels and increased the BUN values compared with TAA animals. Also it was more effective than vitamin E or L-carnitine in these actions. These data show the protective effect of these agents, especially melatonin, against oxidative stress and hepatic damage present in fulminant hepatic failure.     

Effects of L-carnitine on neutrophil-mediated ischemia-reperfusion injury in rat stomach

Reactive oxygen metabolites play an important role in ischemia-reperfusion related gastric injury. Primary sources of reactive oxygen metabolites seem to be the xanthine/xanthine oxidase system and neutrophils accumulating within the reperfused tissue. Tissue myeloperoxidase activity is an important index of neutrophil accumulation. The purpose of the present study was to clarify the effect of L-carnitine on the accumulation of neutrophils and neutrophil-induced gastric mucosal damage in rats exposed to ischemia-reperfusion. Rats were randomly divided into three groups: sham-operated, ischemia-reperfusion and ischemia-reperfusion plus L-carnitine groups. Ischemia was induced by clamping the celiac artery for 30 min and then reperfusion was established for 60 min. Gastric injury was assessed by measuring myeloperoxidase activity in gastric tissue. The neutrophil accumulation and hemorrhagic lesions due to ischemia-reperfusion in gastric mucosa were ascertained in a histological study. L-Carnitine (100 mg kg(-1)) administrated intravenously 5 min before ischemia significantly reduced both the gastric injury and myeloperoxidase activity compared with the ischemia-reperfusion group. The results suggest that L-carnitine provides marked protection against ischemia-reperfusion-related gastric injury which could be due to its ability to reduce neutrophil accumulation in ischemic tissue.     

Release of ischemia in paced rat Langendorff hearts by supply of L-carnitine: Role of endogenous long-chain acylcarnitine

Rat Langendorff hearts perfused with media that do not contain erythrocytes or fluorocarbon as oxygen carriers are borderline aerobic during 5 Hz pacing. This follows from the release of catabolic products measured: lactate, urate and lysophosphatidylcholine (IysoPC). Addition of L-carnitine to the perfusion medium reduced the level of these compounds, while the release of long-chain acylcarnitine (LCAC) increased. Previously, we found (Biochem Biophys Acta 847:62–66,1985) that micromolar LCAC protects membranes during reperfusion after ischemia, Therefore, the observed inverse relation between LCAC and the other compounds measured suggests that LCAC is the basis of an acute relief of imminent ischemia by carnitine addition. LCAC may be released from various cell types, including vascular endothelium, as demonstrated. The cationic amphiphilic nature of LCAC is responsible for protection of membrane functions in imminent ischemia. (Mol Cell Biochem 156: 87-91, 1996)     

A Micro-analytical Method for the Determination of Starch and Amylose/Amylopectin Content in Pea Seeds

New modifications of the method for pea starch and amylose/amylopectin analysis were tested with small samples size of smooth and wrinkled peas. The milling process of the sample and preliminary extraction with 40 % ethanol were very important and affected markedly the standard deviation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Protective effect of L-carnitine on testicular ischaemia-reperfusion injury in rats

Testicular torsion is a urological emergency referred to as 'acute scrotum', because inappropriate treatment can lead to male subfertility and infertility. A possible cause of testicular damage is the ischaemia-reperfusion (I/R) injury attributed to oxygen free radicals. L-carnitine, a vitamin-like antioxidant, plays a pivotal role in the maturation of spermatozoa within the reproductive tract. The aim of the present paper was to determine the protective effect of L-carnitine on testicular I/R-induced injury. Thirty-two male rats were divided into 4 groups (n = 8). Testicular torsion was created by rotating the right testis 720 degrees in a clockwise direction. Group 1: sham-operated control; group 2: ischaemia; group 3: I/R; group 4: ischaemia-L-carnitine treatment-reperfusion group. L-carnitine (500 mg kg(-1), intraperitoneally) was administered before 30 min of detorsion in Group 4. After torsion (5 h) and detorsion (5 h), bilateral orchidectomy was performed. The malondialdehyde (MDA) level was evaluated in testes. Histopathologically, Johnsen's spermatogenesis criteria and mean seminiferous tubule diameter (MSTD) measurements were used. Testicular MDA levels were higher in the torsion group compared to the sham-control group (p < 0.05). Detorsion (reperfusion) caused a further increase in MDA levels (p < 0.05). Pretreatment with L-carnitine prevented a further increase in MDA levels (p < 0.05). Histologically, torsion caused some separation among germinal cells in the seminiferous tubules, which became much more prominent in the I/R group but was attenuated with L-carnitine pretreatment. In conclusion, L-carnitine pretreatment may have a protective effect in experimental testicular torsion-detorsion model in rats by its well-known antioxidant potential.     

海洋微生物裂解二甲基巯基丙酸内盐(DMSP)的酶促催化机制

二甲基巯基丙酸内盐(dimethylsulfoniopropionate,DMSP)是全球硫循环和碳循环的重要载体物质。海洋浮游植物、大型藻类和临海被子植物是DMSP的主要生产者。每年DMSP的产量可以达到1×10~9吨。在北大西洋表面的某些区域,DMSP的产量可以达到碳固定总量的10%。微生物介导的DMSP的裂解是全球硫循环和碳循环的重要步骤。目前,8种参与裂解DMSP的DMSP裂解酶已被报道。在已发现的8种DMSP裂解酶中,3种DMSP裂解酶的催化机制得到了研究和阐明。本文根据国内外研究成果,主要对DMSP裂解过程的酶促催化机制的研究进展进行综述,认为在今后工作中需要继续发现新的DMSP裂解酶,并进一步揭示海洋微生物裂解DMSP的分子机制。     

辣椒素的荧光分析方法研究

荧光分光光度法可用于辣椒及高纯度辣椒素样品中辣椒素的定量分析。在Ex为278 nm,Em为312 nm荧光条件下,辣椒素在0.58-5.8μg/mL浓度范围内其浓度C(μg/mL)与荧光强度I具有良好线性关系,回归方程c=1.0377×10-3I-0.3667,R=0.9994,精密度RSD=0.08%(n=5)。平均回收率95.39%。     

酶-DNS比色法测定酵母海藻糖的研究

确定了以酶-DNA比色法定量测定酵母海藻糖的方法,并对可能影响测定的因素进行了研究。结果表明：酶-DNA比色法无设备条件要求限制,且快速,准确,特异性强。     

Direct measurement of enantiomeric ratios of enzymatic resolution by chiral high-performance liquid chromatography

(R)- and (S)-Methyl 2-(phenoxy)propionate and their acids could be separated simultaneously by a Chiralcel OD or OK column, while (R)- and (S)-methyl 2-(4-chlorophenoxy)propionate and their acids were separated concurrently only by an OK column. This is a novel and facile way to measure the enantiomeric excesses of the remaining substrate and product in the reaction of enzymatic resolution; enantiomeric ratios could then be calculated.