Enzymic acylation of 6-aminopenicillanic acid

The enzymic synthesis of benzylpenicillin from 6-aminopenicillanic acid in the presence of poly (ethylene glycol) has been studied. With equimolar initial concentrations (20 mM) of 6-aminopenicillanic acid and phenylacetic acid a 60% conversion to benzylpenicillin can be achieved at 10°C and pH 5.2 in the presence of 45% (w/v) poly(ethylene glycol). Under these conditions the lactam ring of the benzylpenicillin and 6-aminopenicillanic acid and the enzyme, penicillin acylase (penicillin amidase, penicillin amidohydrolase, EC 3.5.1.11), were more stable than in the absence of the polyol.     

Ultrasonic pretreatment for lipase-catalyzed synthesis of 4-methoxy cinnamoyl glycerol

4-Methoxy cinnamoyl glycerol (4MCG) is a very promising UV filters material in personal care products. In order to effectively improve the yield of 4MCG, a systematic study on ultrasonic pretreatment enzymatic esterification for 4MCG products was carried out. An ultrasonic frequency of 35 kHz, ultrasonic power of 150 W and ultrasound irradiation time of 1.5 h was determined to guarantee satisfactory degree of esterification and lipase activity. The optimum production was achieved in organic solvent system at 65 °C with 4MCA to glycerol molar ratio of 1:5, enzyme amount of 15 mg/mL, resulting in a monoester yield of above 66% and 55% after 48 h and 24 h of reaction under ultrasonic pretreatment, respectively. The experimental kinetic data were studied. The reactions were modeled by a system of sequential first-order rate expressions, kinetic parameters were estimated from experimental data fit to the model equations. Results show that the monoester yield in the ultrasonic pretreatment process (24 h) were above 1.5-fold as that in mechanical stirring process without essential damaging to lipase activity. The enzymatic method using ultrasonic pretreatment was obviously superior to the mechanical stirring for enzymatic method and chemical method in terms of conversion rate and the monoester yield. These results are of great significance for applying ultrasonic pretreatment method to prepare 4MCG.     

Synthesis of thio-and selenophospholipids from 2,2,5,5-Tetra(hydroxymethyl)cyclopentanone

New phospholipids, thio-and selenoanalogues of phosphatidic acids, were synthesized on the basis of 2,2,5,5-tetra(hydroxymethyl)cyclopentanone. The starting tetraol monoketal was phosphorylated with amidophosphorous acid chlorides to protected polyol amidophosphites, which were further sulfurized or selenized to phosphoacetals. These were directly acylated with fatty acid chlorides to thio-and selenoanalogues of phospholipids.     

Genetic variation in ZmTIP1 contributes to root hair elongation and drought tolerance in maize

Drought is a major abiotic stress that threatens maize production globally. A previous genome‐wide association study identified a significant association between the natural variation of ZmTIP1 and the drought tolerance of maize seedlings. Here, we report on comprehensive genetic and functional analysis, indicating that ZmTIP1, which encodes a functional S‐acyltransferase, plays a positive role in regulating the length of root hairs and the level of drought tolerance in maize. We show that enhancing ZmTIP1 expression in transgenic Arabidopsis and maize increased root hair length, as well as plant tolerance to water deficit. In contrast, ZmTIP1 transposon‐insertional mutants displayed the opposite phenotype. A calcium‐dependent protein kinase, ZmCPK9, was identified as a substrate protein of ZmTIP1, and ZmTIP1‐mediated palmitoylation of two cysteine residues facilitated the ZmCPK9 PM association. The results of this research enrich our knowledge about ZmTIP1‐mediated protein S‐acylation modifications in relation to the regulation of root hair elongation and drought tolerance. Additionally, the identification of a favourable allele of ZmTIP1 also provides a valuable genetic resource or selection target for the genetic improvement of maize.     

Immobilized Pseudomonas sp. lipase: A powerful biocatalyst for asymmetric acylation of (±)-2-amino-1-phenylethanols with vinyl acetate

Pseudomonas sp. lipase was immobilized onto glutaraldehyde-activated Florisil^® support via Schiff base formation and stabilized by reducing Schiff base with sodium cyanoborohydride. The immobilization performance was evaluated in terms of bound protein per gram of support (%) and recovered activity (%). A 4-factor and 3-level Box–Behnken design was applied for the acylation of (±)-2-(propylamino)-1-phenylethanol, a model substrate, with vinyl acetate and the asymmetric acylations of other (±)-2-amino-1-phenylethanols with different alkyl substituents onto nitrogen atom such as (±)-2-(methylamino)-1-phenylethanol, (±)-2-(ethylamino)-1-phenylethanol, (±)-2-(butylamino)-1-phenylethanol and (±)-2-(hexylamino)-1-phenylethanol were performed under the optimized conditions. The optimal conditions were bulk water content of 1.8%, reaction temperature of 51.5 °C, initial molar ratio of vinyl acetate to amino alcohol of 1.92, and immobilized lipase loading of 47 mg mL^?1. (R)-enantiomers of tested amino alcohols were preferentially acylated and the reaction purely took place on the hydroxyl group of 2-amino-1-phenylethanols. The increase of alkyl chain length substituted onto nitrogen atom caused an increase in the acylation yield and ee values of (S)-enantiomers. Enantiomeric ratio values were >200 for all the reactions. Our results demonstrate that the immobilized lipase is a promising biocatalyst for the preparation of (S)-2-amino-1-phenylethanols and their corresponding (R)-esters via O-selective acylation of (±)-2-amino-1-phenylethanols with vinyl acetate.     

Kinetically controlled synthesis of monoglyceryl esters from chiral and prochiral acids methyl esters catalyzed by immobilized Rhizomucor miehei lipase

Partial acylation of only one primary hydroxyl group of glycerol generates a chiral center at position 2. Rhizomucor miehei lipase (RML) catalyzes the kinetically controlled transesterification of different aromatic carboxylic acids methyl esters with glycerol. High synthetic yields of glyceryl esters (around 70-80%) were obtained even in the presence of significant concentrations of water (from 5% to 20%). After a long incubation of the reaction mixture in the presence of the biocatalyst only pure free acid was obtained. Other lipases (from Geobacillus thermocatenulatus and from Thermomyces lanuginose) also catalyzed similar kinetically controlled transesterifications although less efficiently. RML immobilized on Sepharose-Q showed a high activity and specificity, compared to the immobilization by other techniques, only producing monoglyceryl esters with all substrates. In particular, monoglyceryl-phenylmalonate product was synthesized in 82% overall yield and >99% diastereomeric excess at pH 7.0 and 37 °C and 90% glycerol.     

Regioselective one pot synthesis of 3,3'-diindolylethylene derivatives and study of their cytotoxic activity

2,2′-Diphenyl-3,3′-diindolylethylene (DPDIE) derivatives 3a-g were regioselectively prepared in one pot from indoles 1a-g in the presence of Lewis acids and were subsequently evaluated for cytotoxic activity against human leukemic cell lines, U937 and K562. The most potent compound 3g exhibited IC₅₀ of 13.0-17.0 μM.     

New insights into the regulation of plant immunity by amino acid metabolic pathways

Besides defence pathways regulated by classical stress hormones, distinct amino acid metabolic pathways constitute integral parts of the plant immune system. Mutations in several genes involved in Asp‐derived amino acid biosynthetic pathways can have profound impact on plant resistance to specific pathogen types. For instance, amino acid imbalances associated with homoserine or threonine accumulation elevate plant immunity to oomycete pathogens but not to pathogenic fungi or bacteria. The catabolism of Lys produces the immune signal pipecolic acid (Pip), a cyclic, non‐protein amino acid. Pip amplifies plant defence responses and acts as a critical regulator of plant systemic acquired resistance, defence priming and local resistance to bacterial pathogens. Asp‐derived pyridine nucleotides influence both pre‐ and post‐invasion immunity, and the catabolism of branched chain amino acids appears to affect plant resistance to distinct pathogen classes by modulating crosstalk of salicylic acid‐ and jasmonic acid‐regulated defence pathways. It also emerges that, besides polyamine oxidation and NADPH oxidase, Pro metabolism is involved in the oxidative burst and the hypersensitive response associated with avirulent pathogen recognition. Moreover, the acylation of amino acids can control plant resistance to pathogens and pests by the formation of protective plant metabolites or by the modulation of plant hormone activity.     

Inhibition of Iron/Ascorbate-Induced Lipid Peroxidation by an N-Terminal Peptide of Bovine Lactoferrin and Its Acylated Derivatives

Bovine lactoferrin (LF) and lactoferricin B (LFcin B), an antimicrobial peptide derived from bovine LF, inhibited thiobarbituric acid-reactive substance (TBARS) formation in a iron/ascorbate-induced liposomal phospholipid peroxidation system. The inhibition of TBARS formation occurred with N-acylated 9-mer peptides with a core sequence of LFcin B and, compared to LFcin B, their antioxidant effect was clearly observed at a concentration almost 100 times lower.