Enantioselective hydrolysis of racemic methyl jasmonate using microorganisms and isolated enzymes

A variety of microorganisms were used to hydrolyze racemic methyl jasmonate [I] with varying degrees of enantioselectivity. The fungi tested included species from the genera Aspergillus, Penicillium, and Talaromyces. All fungi tested showed a preference for the [1S,2S(Z)]-(+)-isomer. The yeasts Saccharomyces cerevisiae and Candida albicans showed no activity. A number of bacterial genera were also tested. No activity could be shown for members of the genera Bacillus, Pseudomonas, Escherichia, Nocardia, and Thermoactinomyces. Hydrolytic activity was found in the genera Streptomyces and Mycobacterium. S. henetus showed the same enantioselectivity as the fungi, while M. phlei hydrolyzed the [1R,2R(Z)]-(−)-isomer preferentially. A number of isolated enzymes were also screened for activity. Varying degrees of hydrolytic activity and enantioselectivity were found.     

Effects of autoclave-induced carbohydrate hydrolysis on the growth ofBeta vulgaris cells in suspension

Media of de Greef & Jacobs (1979) were autoclaved either with all the nutrient components in a single vessel (medium 1) or with the following components in separate vessels: FeNa–EDTA+CaCl₂ (medium 2), FeNa–EDTA+NaH₂PO₄ (medium 3) or sucrose (medium 4). Medium 5 was prepared by autoclaving FeNa–EDTA+NaH₂PO₄ and sucrose in two separate vessels. It was found that the dry mass yield of cell suspensions ofBeta vulgaris was lowest in medium 1, followed by media 2 and 3. There was no significant difference among media 3, 4, and 5.The plot of dry mass yield of the cell suspensions against the rates of cyanide-initiated oxygen consumption which indicate the extent of carbohydrate hydrolysis of the media during autoclaving, indicated the presence of a threshold rate of about 17–20 nmol ml^–1 min^–1. Dry mass yield of the suspensions decreased rapidly when the rate exceeded this value.For media with glucose as the source of carbohydrate, the rate of cyanide-initiated oxygen consumption exceeded the threshold value by a factor of 1.5 to 2, depending on the volume of the media autoclaved.Abbreviations FeNa-EDTA ferric monosodium ethylenediamine-tetraacetic acid     

Aging of the erythrocyte

In contrast to situation found in other cell types, no linear dependence of product fluorescence vs time is observed when fluoresceine diacetate (FDA) is hydrolysed by erythrocytes and hemolysates. The rate of hydrolysis is increased by high concentrations of sucrose suggesting a positive effect of viscosity on the rate of the reaction. These peculiarities can be explained by assumption of a two-step hydrolysis of FDA. The FDA-hydrolytic activity decreases with increasing cell density (age).     

Studies on the hydrolysis of 3-methyl-2′-deoxycytidine in aqueous solution A synthesis of 3-methyl-2′-deoxyuridine

The hydrolysis of 3-methyl-2′-deoxycytidine in aqueous solution has been investigated. Varying proportions of 3-methylcytosine, 3-methyluracil and 3-methyl-2′-deoxyuridine are formed depending upon conditions of pH and temperature. All three hydrolytic products are formed at pH 6.8 and 90°C. At pH 2, depyrimidination of 3-methylcytosine occurs as the only hydrolysis product. When the pH is increased to 12, 3-methyl-2′-deoxycytidine on heating at 90°C is completely deaminated to 3-methyl-2′-deoxyuridine with few side products formed. This reaction serves as the basis for a convenient synthesis of 3-methyl-2′-deoxyuridine. The 300 MHz spectra of 3-methyl-2′-deoxycytidine and 3-methyl-2′-deoxyuridine indicate that the sugar ring in these compounds is predominantly in ²E conformation.     

Hydrolysis of Galactose from Glycolipids and Glycoprotein by Young Rat Brain β-Galactosidases Immobilized to Sepharose 4B

An extract of glycosidic enzymes from young rat brain was immobilized to cyanogen bromide-activated Sepharose 4B. Most glycosidases retained approximately 10-25% of their activities after immobilization. Immobilized β-galactosidases were used repeatedly without detectable loss of enzyme activity in the hydrolysis of p-nitrophenyl-β-d -galactopyranoside. In addition to the synthetic substrate, the immobilized rat brain β-galactosidases could also hydrolyze galactose from lactose, galactosylcerebroside, asialofetuin, and GM₁-ganglioside. The hydrolysis of GM₁- to GM₂-ganglioside was confirmed on TLC.     

β-structures of polypeptides with L- and D-residues

Summary It was previously shown that nuclei of-sheets surrounded by unordered segments are formed in polypeptide chains built up with alternating hydrophobic and hydrophilic residues and containing both L- and D-enantiomers. It was also established that segments of residues having the same configuration tend to segregate in these nuclei when the starting composition of stereomonomers departs from the racemic mixture.Soft acidic hydrolysis of these polymers has been studied. Kinetic measurements show two pseudo first order rate constants, in agreement with the existence of two conformational species. The unordered part of the chains is hydrolyzed more rapidly, allowing the isolation of a-fraction enriched in one enantiomer. Thus, a plausible process of enrichment in enantiomer during prebiotic evolution has been described, which however does not explain the preference of one enantiomer over the other one.     

Physiological and biochemical contributions to the taxonomy of the genera Ankistrodesmus and Scenedesmus

The 17 Ankistrodesmus strains studied do not produce extracellular amylolytic enzymes. 20 out of 28 Scenedesmus strains, however, are able to hydrolyse starch.The groups of strains previously characterized physiologically and biochemically were assigned to established species of the genera Ankistrodesmus (including Monoraphidium) and Scenedesmus.Abbreviation GC Guanine + cytosine     

Investigation of the operational stabilities and kinetics of glucoamylase immobilized on alkylamine derivatives of titanium(IV)-activated porous inorganic supports

Glucoamylase (exo-1,4-α-d-glucosidase, EC 3.2.3.1) was coupled to several porous silica matrices by an improved metal-link/chelation process using alkylamine derivatives of titanium(IV)-activated supports. In order to select the titanium activation procedure which gave stable enzyme preparations, long-term stability tests were performed. The immobilized glucoamylase preparations, in which the carrier was activated to dryness with a 15% w/v TiCl₄ solution, displayed very stable behaviour, with half-lives of ～60 days. The optimum operating conditions were determined for these preparations. There are significant differences between the behaviour of the immobilized enzyme and the free enzyme. The apparent K_m increased on immobilization due to diffusional resistances. The pH optimum for the immobilized preparation showed a slight shift to acid pH relative to that of the soluble enzyme. Also, the optimum temperature descreased to 60°C after immobilization. In order to test Michaelis-Menten kinetics at high degrees of conversion, time-course analysis of soluble starch hydrolysis was performed. It was observed that simple Michaelis-Menten kinetics are not applicable to the free/immobilized glucoamylase-starch system at high degrees of conversion.     

Hydrolysis of cyclosporin A: Identification of 1,11 seco-cyclosporin A and 4,5 secoisoCyclosporin A by FAB-MS/MS

We have previously reported that treatment of CsA with aqueous HCl gives rise to the formation of a number of water-soluble compounds. Two of these were identified from their FAB-MS/MS spectra as open-chain nona- and decapeptides. We describe here the identification of two other main compounds deriving from the same treatment. Identification was rendered possible from the comparison of their FAB-MS/MS spectra with those of methyl and acetyl derivatives. The two compounds are water-soluble, open-chain undecapeptides corresponding to 1,11 seco-CsA and of 4,5 seco-isoCsA, respectively.     

Stereoselective Synthesis of (S,E)-6-Isopropyl-3,9-dimethyl-5,8-decadienyl Acetate,the (S)-Enantiomer of the Yellow Scale Pheromone

The (S)-enantiomer of the sex pheromone of the yellow scale (Aonidiella citrina), (S,E)-6-isopropyl-3,9-dimethyl-5,8-decadienyl acetate, was stereoselectively synthesized from (R)-(+)-citronellic acid.