Esterases in mycobacteria

It was found that a submerged culture ofMycobacterium phlei degrades simple esters (ethylacetate and ethylbutyrate) as well as synthetic lipids (triacetine and tributyrine). The effect of pH on the rate of degradation of tributyrine was investigated and the maximum activity of esterases found within a wide range of pH. The activity of esterases was followed during growth of a submerged culture ofMycobacterium phlei. Esterases were not released into the cultivation medium during growth or even during the early stationary phase. Only a low steady activity of esterases could be demonstrated in a filtrate of the cultivation liquid. The total activity of esterases reached its maximum after a 6–11 day incubation. The specific activity of esterases reached a maximum on the 6th day of incubation; its value decreased to about one half and did not change substantially on prolonged incubation. Changes in the specific activity of esterases were found to be time-related with changes of pH and a decrease of the specific activity was associated with a release of macromolecular compounds into the incubation medium. Esterases as well as other macromolecular compounds were isolated from the filtrate of the cultivation medium ofMycobacterium phlei. The isolated preparation contained 60–72% total activity of esterases present in the filtrate of the cultivation liquid.     

Esterases in mycobacteria

A procedure for the isolation of a crude enzyme preparation of esterases fromMycobacterium phlei was worked out. The procedure consists in breaking cells in 1% KCl by ultrasonication, ultracentrifugation at 40,000 r.p.m. and isolation of acetone and ether dried enzyme preparation. Specific activity increased 2.8-fold after completion of the procedure. Esterases fromMycobacterium phlei were separated on Sephadex of G series to two enzymes with different substrate specificity. The first enzyme, acetic ester acetyl-hydrolase (E.C. 3.1.1.6) was found to be relatively specific for ethylacetate, the second, carboxylic ester hydrolase (E.C. 3.1.1.1) for ethylbutyrate and tributyrine. Preparations of both enzymes were made from the crude extracts of cells and from a mixture of macromolecular compounds isolated from the culture filtrate ofMycobacterium phlei.     

Esterases in mycobacteria

Esterases ofMycobacterium phlei (acetic ester acetyl hydrolase E.C.3.1.6 and carboxylic esterhydrolase E.C.3.1.1.1.) obtained after separation on Sephadex G-100 can be temporarily, for a short time interval, activated by adding calcium ions. The activation of esterases isolated from cells was non-repeteable, whereas the temporary activation of esterases from the culture filtrate could be repeated by increasing concentrations of calcium ions. However, the value of activation gradually decreased. Similarly with calcium ions strontium ions were also effective, however, higher concentrations were required and the activation was non-repeatable. Magnesium ions were practically without any effect. Possible mechanisms of the temporary activation of esterases ofMycobacterium phlei are discussed.     

Lipolytic Esterases in Staphylococci

Staphylococci split a wide range of lipid substrates by production of an enzyme complex with two main components (i) a lipase acting optimally on fat-soluble glycerides, and (ii) an esterase acting optimally on water-soluble esters. The action is dependent upon carbon chain length, interfacial dispersion, solubility, and pH of substrate and end products. The esterase is less susceptible to organophosphorus inhibitors than mammalian esterases. There is no apparent correlation between lipolysis and markers of pathogenicity such as production of coagulase and toxin, but the possession of a flexible lipolytic mechanism might account for the persistence of staphylococci in the fatty secretions of mammalian skin.     

细菌酯酶研究进展

酯酶(esterase)是一类催化酯键水解和合成的酶的总称,水解时催化酯键产生甘油和脂肪酸,合成时把酸的羧基与醇的羟基脱水缩合,产物为酯类及其他芳香类物质。酯酶广泛存在于动物、植物和微生物中。微生物酯酶在细菌中分布最多,广泛存在于包括链球菌、金黄色葡萄球菌、新型隐球菌、绿脓杆菌、结核杆菌等多种细菌中。目前关于酯酶和细菌毒力作用的相关性研究正处于起始阶段。本文对酯酶的结构、分类、作用机制、基因调控,以及一些代表性细菌酯酶的具体研究进展进行综述。     

Esterases in histochemistry and ultrahistochemistry

Synopsis The histochemical identification of individual esterases is a problem that has not yet been overcome. Inhibitors and different substrates reveal different patterns of distribution. 8-hydroxyquinoline acetate is a useful substrate in ultrahistochemistry. There is evidence of a relationship between esterase distribution and function.ACTH adrenocorticotropic hormone - 5Bri–O-2 5-bromoindoxyl acetate - 5Br–4ClI–O-2 5-bromo-4-chloro indoxyl acetate - cAMP cyclic adenosine monophosphate - DFP di-isopropyl-fluorophosphate - hCG human chorion gonadotropin - HS-2/4 thiol acetate/butyrate - I-O-2/4 indoxyl acetate/butyrate - N-O-2/3/4 -naphthyl acetate/propionate/butyrate - N-O-2 -naphthyl acetate - N-S-2/9 -naphthyl thiolacetate/nonanoate - NAS-O-2 naphthol AS acetate - NASD-O-2 naphthol AS-D acetate - 4NP-O-2/3 p-nitrophenyl acetate/propionate - 4NP-S-2 p-nitrophenyl thiol acetate - P-O-2 phenyl acetate - Q-O-2/4 8-hydroxyquinoline acetate/butyrate - Q-S-2/4 8-mercaptoquinoline acetate/butyrate - TBA-S-2/9 -thiolbenzanilide acetate/nonanoate - TSH thyroid-stimulating hormone     

Esterases of developing human brain

Abstract The free and bound nonspecific esterases occurring in, respectively, the saline and triton X-100 extracts of adult and developing human brain were studied by starch gel electrophoresis (zymograms). Zymograms of the free esterase fraction visualized with NA as substrate were qualitatively similar at 5-12 days of age to the electrophoretic patterns observed in adult material. In both adult and developing brain, zymograms of bound esterase resembled those of the free enzyme, the major difference being the presence in the former of a slow, broad, anodic zone of diethyl-p-nitrophenyl phosphate-inhibited enzyme. Esterases characteristic of adult white matter and having preferential affinity for alpha-naphthylpropionate, alpha-naphthyl butyrate and alpha-naphthyl valerate were not identified in infant brain until about 4 months postnatal age. A far-moving, anodic enzyme was distinctly evident in zymograms of brains of less than 1 month of age. This enzyme hydrolysed NP, NB, and NV more actively than alpha-naphthyl acetate. It was present in the adult brain but, in contrast to the infant, was no longer electrophoretically-separable from another enzyme which had greater affinity for NA and had previously been designated the A₁₀ band. Quantitative assays demonstrated that the bound esterase increased in cerebral and cerebellar cortex during development. In contrast, the proportion of free to bound esterase showed little change in white matter. Acetylcholinesterase and butyrylcholinesterase zymograms became identical to adult patterns from 1 to 4 months of age. Thiolacetic acid esterase was present at 38 weeks gestation. Some functional and anatomical correlations were attempted in explanation of the biochemical observations.     

Esterases in pollen and stigma of Brassica

The dry type stigma of Brassica is covered with a continuous layer of cuticle. Cutinase and non-specific esterases may be involved in breakdown of this cuticle barrier during pollen-stigma interaction, but only a little is known about their nature and characteristics. We report here the presence of two distinct esterases from stigma and pollen of Brassica. A 33 kD esterase assayed using MU-butyrate substrate shows high activity in stigma papillae. A similar esterase from Tropaeolum pollen has been shown to possess active cutinase activity. The esterase activity in anther tissue is due to a 24 kD enzyme with substrate specificity toward acetate esters. Both enzymes require sulfhydryl groups for their catalytic activity. Immunogold labelling of antibodies raised against these esterases localised the proteins at the subcellular level. Antibodies for MU-butyrate hydrolase gave a positive signal in the cell walls of mature stigma papillae and in the tapetum and microspores during early stages of anther development. In the mature anther, a positive signal in the cytoplasm of pollen grains with some detectable localisation in the exine layer of the pollen wall was obtained. Similar results were obtained with acetate hydrolase antibodies. These esterases are thus spatially and temporally regulated in stigma and anther tissues.Abbreviations MU methyl umbelliferyl - pAbC anti-butyrate hydrolase polyclonal antibodies - pAbE anti-acetate hydrolase polyclonal antibodies     

Recombination in mycobacteria

Mycobacterium tuberculosis , the causative agent of tuberculosis (TB) is thought to infect a quarter of the world's population and accounts for 3 million deaths each year. Leprosy, caused by Mycobacterium leprae continues to afflict millions. In many countries, the incidence of TB is increasing due to its association with acquired immune deficiency syndrome (AIDS) and the emergence of multidrug resistance strains of tubercle bacilli. Genes that encode major antigens, enzymes, potential virulence determinants and drug resistance in mycobacteria have been isolated and characterized; however, further genetic analysis of pathogenic mycobacteria has been severely hampered by the difficulty in precisely defining the phenotype of both wild-type and mutant genes by utilizing homologous recombination to perform allele exchange. Recombination mechanisms have been intensely studied in Escherichia coli but it is unclear how far mechanistic pathways elucidated in this species are applicable to other organisms, such as mycobacteria. The aim of this review is to examine what is currently known about homologous recombination in mycobacteria. A model is proposed to account for both low levels of homologous recombination and high levels of illegitimate recombination found in the tubercle bacillus.     

Surrounded by mycobacteria: nontuberculous mycobacteria in the human environment

A majority of the Mycobacterium species, called the nontuberculous mycobacteria (NTM), are natural inhabitants of natural waters, engineered water systems, and soils. As a consequence of their ubiquitous distribution, humans are surrounded by these opportunistic pathogens. A cardinal feature of mycobacterial cells is the presence of a hydrophobic, lipid-rich outer membrane. The hydrophobicity of NTM is a major determinant of aerosolization, surface adherence, biofilm-formation, and disinfectant- and antibiotic resistance. The NTM are oligotrophs, able to grow at low carbon levels [>50 μg assimilable organic carbon (AOC) l⁻¹], making them effective competitors in low nutrient, and disinfected environments (drinking water). Biofilm formation and oligotrophy lead to survival, persistence, and growth in drinking water distribution systems. In addition to their role as human and animal pathogens, the widespread distribution of NTM in the environment, coupled with their ability to degrade and metabolize a variety of complex hydrocarbons including pollutants, suggests that NTM may be agents of nutrient cycling.     

The genetics of some polymorphic Esterases in Drosophila simulans

Analysis of strains of Drosophila simulans derived from a natural population in Turkey has shown that three alleles at the Esterase-6 locus are present in some strains. These alleles produce allozymes with mobilities equivalent to other esterases coded for by three other loci, one of which () is tightly linked to Esterase-6. Active alleles at all these loci are present at low frequencies. The presence of the active allele at the locus in laboratory strains in absolutely correlated with the presence of the Esterase 6 ^-3 allele and strong linkage disequilibrium between these two loci exists.It appears possible that the origin of one or more of these hitherto unremarked loci, whose active alleles are expressed only in females, lies in gene duplication, coupled with the action of selection in an environment thought to be heavily     

'Atypical' mycobacteria in milk

Seventy-seven isolates of 'atypical' mycobacteria were obtained from 288 raw milk samples but no isolates were made from 76 samples of pasteurized milk. Thirty-two clinically important 'atypical' mycobacteria were isolated.