Selectivity is an Important Characteristic of Lipases (Acylglycerol Hydrolases)

Lipases are enzymes that usually hydrolyze acylglycerols, but will hydrolyze the carboxylic esters in many other compounds. They also catalyze esteriftcations and transesterifications. In addition to specificity for carboxylic esters, the lipases are selective for lipid classes and show selectivity for primary vs. secondary alcohols (positional or regio-), fatty acids, enantiomers (chirality of either the acid or alcohol residue) and combinations of these. Uses of the enzymes have depended to some extent on regio- and fatty acid selectivities. Newer applications, such as ester synthesis and asymmetric hydrolysis, may not be based on selectivities. Factors affecting selectivities are discussed and some areas for research are mentioned.     

Ultrastrukturen Und Cytochemie Der Pellikula Und Des Apikalkomplexes Der Kineten Von Babesia Bigemina Und Babesia Ovis In Hämolymphe Und Ovar Von Zecken*,†

SYNOPSIS The term kinete is used in this paper for the cigar-shaped, motile development stages (“vermicule”) of Babesia occurring intra- and extracellularly in hemolymph and ovary (including oocytes) of vectors, hard ticks (Ixodoidea). The structure of, and cyto-chemical activities of hydrolases (acid phosphatase, nonspecific esterase) in the pellicle and the apical complex were studied at the fine-structural level in kinetes of Babesia bigemina Smith & Kilborne, in hemolymph of female Boophilus microplus Canestrini. The cytochemistry of acid hydrolases was studied also in kinetes of Babesia ovis (Babes) Starcovici, in hemolymph and ovary of Rhipi-cephultis bursa Canestrini & Fanzago. The pellicle of the B. bigemina kinetes is composed of 3 membranes (pellicular complex): an outer membrane, ?8 nm thick (the plasmalemma) and 2 inner ones, each ?6 nm thick, lying closely together. The outer membrane appears to be covered by a structureless coat, 3 nm thick. The space between the inner double membrane and the plasmalemma is 7.5 nm. The whole pellicular complex is 30 nm in diameter. The 2 inner pellicular membranes appear to be derived from the endoplasmic reticulum (ER) for the following reasons: (a) a layer of hydrolase-active material is enclosed by these membranes; (b) in the spheroid parasite stages which transform from kinetes inside hemocytes, the inner double membrane is apparently replaced by an ER cisterna; (c) the thickness of each of the inner pellicular membranes is approximately the same as that of the ER membrane. There are circular openings in the pellicular double membrane with average diameters of 100 nm; despite some similarity to micropores, they have a specific structure. The term Intrapellikularfenster (IPF) (intrapellicular windows) or pseudomicropores is proposed for these pellicular differentiations. The margin of an FPF is formed by the 2 inner membranes folding into each other; cytoplasmic, electron-dense material is accumulated alongside this edge. Unlike that of micropores, the plasmalemma of the IPF is not invaginated. The IPF appears as a single, dark ring in tangential sections. At times, rhoptry-like bodies are associated with the openings. The function of the IPF is not known. An intrapellicular opening similar to the IPF, although wider, is present at the apex of the parasite. Its margin coincides with the inner edge of the apical ring. Typical subpellicular microtubuli were not observed in the Babesia kinetes. The apical complex of the B. bigemina kinetes consists of an Apikalschirm (apical umbrella), a crown of microtubuli beneath it, and rhoptries: micronemes are also present in large numbers. The Apikalschirm is located beneath the pellicle of the apical pole of the parasite. It is a wheel-like structure composed of spokes radiating from a wide, hub-like central ring (apical ring). It should be stressed that the apical ring is not identical with the polar ring described as an integral part of the pellicular complex in other Apicomplexa. Beneath each “rib” of the Apikalschirm there is one microtubule (subcostal microtubule). In kinetes of B. ovis the “ribs” are less well developed. In addition, the Apikalschirm is more pointed in kinetes of this species in tick oocytes and ova. The rhoptries of the kinetes are spindle-shaped and largely located directly beneath the Apikalschirm. They are arranged radially, each row being associated with a “rib”. A conoid was not observed. Occasionally, low hydrolytic activity could be detected in micronemes. The rhoptries and the Apikalschirm were always negative for phosphatase and esterase activity. With regard to the number and arrangement of its membranes and to its hydrolase activity, the pellicle of the kinetes of Babesia closely resembles the pellicular complex of the Coccidia. It differs from the latter by the presence of the IFF and by the lack of micropores and of true subpellicular microtubules. In the complexity of their pellicle and in some details of the organization of their apical complex (lack of a conoid; umbrella-like structure), the kinetes of Babesia resemble the ookinetes of the Haemosporidia.     

蚕豆叶肉原生质体电融合的研究

本文研究了蚕豆叶肉原生质体经透明质酸酶、核糖核酸酶、神经氨酸酶、碱性磷酸酶、胰蛋白酶、脂肪酶六种水解酶和SDS、Triton X-100、CTMAB三种表面活性剂以及秋水仙素、细胞松驰素B处理后的电融合过程。结果表明:胰蛋白酶处理后的原生质体融合率明显下降;碱性磷酸酶、脂肪酶以及核糖核酸酶、透明质酸酶、神经氨酸酶处理的原生质体电融合率均有不同程度的上升。Triton X-100和CTMAB促进原生质体的电融合,但较高浓度(0.01%)的SDS起抑制作用。秋水仙素和细胞松驰素B处理的原生质体其电融合率有较大幅度的增高。     

A novel type of meso-diaminopimelic acid-based peptidoglycan and novel poly (erythritol phosphate) teichoic acids in cell walls of two coryneform isolates from the surface flora of French cooked cheeses

The primary structure of the peptidoglycan and the teichoic acids of two coryneform isolates from the surface flora of French cooked cheeses, CNRZ 925 and CNRZ 926, have been determined. In the peptidoglycan, meso-diaminopimelic acid was localized in position three of the peptide subunit. It contained an d-glutamyl-d-aspartyl interpeptide bridge, connecting meso-diaminopimelic acid and d-alanine residues of adjacent peptide subunits. The -carboxyl group of d-glutamic acid in position two of peptide subunits was substituted with glycine amide. The teichoic acid pattern and composition differed between the strains: both contained an erythritol teichoic acid and strain CNRZ 925 also contained an N-acetylglucosaminylphosphate polymer. The erythritol teichoic acids differed in terms of the quality and quantity of substituents, but they both had N,N-diacetyl-2,3-diamino-2,3-dideoxyglucuronic acid in common.Abbreviations DNP dinitrophenyl - Ery erythritol - Gal galactose - GlcN glucosamine - GlcNAc N-acetylglucosamine - GlcUANAc₂ N,N-diacetyl-2,3-diamino-2,3-dideoxyglucuronic acid - Hex UANAc₂ N,N-diacetyl-2,3-diamino-2,3-dideoxyhexuronic - acid m-Dpm, meso-diaminopimelic acid - Mur muramic acid - MurNAc N-acetylmuramic acid     

Degradation of soluble collagen by ozone or hydroxyl radicals

Collagen exposed to ozone or hydroxyl radicals was degraded in a time- and dose-dependent manner. This degradation was inhibited by free radical scavengers. Furthermore, lower levels of these oxidants did not degrade the molecule, but caused it to become susceptible to proteolytic degradation. We suggest an alternative mechanism by which oxygen-derived free radicals participate in the destruction of extracellular matrix observed during acute lung injury by oxidant gas, in addition to the commonly accepted proteinase-antiproteinase theory of lung injury.     

Effect of 6059-S,a novel oxacephem,on cross-linking reaction of peptidoglycan biosynthesis in Escherichia coli,Pseudomonas aeruginosa and Serratia marcescens

The effect of 6059-S, a novel 1-oxacephem, on peptidoglycan synthesis was investigated using ether-treated cells of Escherichia coli K 12, Pseudomonas aeruginosa KM 338 and Serratia marcescens IFO 12648. The cross-linking reaction of peptidoglycan synthesis in these organisms was inhibited by markedly low concentration of 6059-S.Non-standard abbreviations PBP penicillin binding protein - MIC minimum inhibitory concentration - ETB ether treated bacterial cells - SDS sodium dodecylsulfate     

The effect of nisin on murein synthesis

Nisin inhibits murein synthesis with concomitant accumulation of undecaprenyl-pyrophospho-MurNAc(pentapeptide) (lipid intermediate I). This inhibition is caused by the formation of a complex between the antibiotic and lipid intermediate I. Undecaprenyl-pyrophospho-MurNAc(pentapeptide)-GlcNAc (lipid intermediate II) also forms a complex with nisin. However, when murein synthesis is inhibited by nisin, this latter complex is not formed since lipid intermediate II is no longer synthesized.Abbreviations GlcNAc N-acetylglucosamine - MurNAc N-acetylmuramyl - Pentapeptide Ala--DGlu-Lys-DAla-DAla - C₅₅ undecaprenol Dedicated to Professor Otto Kandler on occasion of his 60th birthday     

The enzymic degradation of lipids resulting from physical disruption of cucumber (Cucumis sativus) fruit

Homogenization of fresh tissue from cucumber fruits results in a loss of endogenous lipid catalysed by acyl hydrolase enzymes. Deacylation of lipids is not accompanied by accumulation of free fatty acids. The levels of both saturated (mainly palmitic) and polyunsaturated (linoleic and linolenic) fatty acids in the lipids are reduced. Losses of the major acyl lipid constituents of cucumber (triacylglycerols and phospholipids) are mainly responsible for the observed hydrolysis. Triacylglycerol acyl hydrolase (lipase), phospholipase D and polar lipid acyl hydrolase enzyme activities were demonstrated. It is suggested that hydrolytic attack on endogenous lipids is the initial event on disruption of cucumber tissue, in the formation of lipid degradation products, amongst which are the volatile carbonyl compounds responsible for the characteristic flavour of cucumber.