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Abstract: Resting cells of Rhodococcus sp. G20 were used for the transformation of β-aminopropionitrile to β-alanine, an important beta amino acid. A 23 central composite experimental design was performed with the purpose of optimizing the β-alanine production in a bubble column reactor with 200mL working volume using response surface methodology (RSM). The individual and interactive effects of three independent variables (cells loading, substrate concentration, airflow rate) on β-alanine production were investigated. A quadratic polynomial predictive model was obtained after statistical analysis to predict the optimum biotransformation conditions. The optimum bioconversion conditions of β-aminopropionitrile in a batch operation for β-alanine production were as follows: cells loading of 16.50gww/200mL, substrate concentration of 1.29% (v/v), and airflow rate of 86.56L/h, under which an overall 40.6% increase in productivity of β-alanine was obtained. The influences of the temperature and pH on the conversion were also studied, and the optimums were 30°C and pH 7.5. The measured activation energy (E a) was found to be 22,199J/mol, thus indicating the presence of diffusional resistance. [Copyright &y& Elsevier]

Sortase A (SrtA)‐mediated ligation, a popular method for protein labeling and semi‐synthesis, is limited by its reversibility and dependence on the LPxTG motif, where "x" is any amino acid. Here, we report that SrtA can mediate the efficient and irreversible ligation of a protein/peptide containing a C‐terminal thioester with another protein/peptide bearing an N‐terminal Gly, with broad tolerance for a wide variety of LPxT‐derived sequences. This strategy, the thioester‐assisted SrtA‐mediated ligation, enabled the expedient preparation of proteins bearing various N‐ or C‐terminal labels, including post‐translationally modified proteins such as the Ser139‐phosphorylated histone H2AX and Lys9‐methylated histone H3, with less dependence on the LPxTG motif. Our study validates the chemical modification of substrates as an effective means of augmenting the synthetic capability of existing enzymatic methods. [ABSTRACT FROM AUTHOR]

Sortase A (SrtA)‐mediated ligation, a popular method for protein labeling and semi‐synthesis, is limited by its reversibility and dependence on the LPxTG motif, where "x" is any amino acid. Here, we report that SrtA can mediate the efficient and irreversible ligation of a protein/peptide containing a C‐terminal thioester with another protein/peptide bearing an N‐terminal Gly, with broad tolerance for a wide variety of LPxT‐derived sequences. This strategy, the thioester‐assisted SrtA‐mediated ligation, enabled the expedient preparation of proteins bearing various N‐ or C‐terminal labels, including post‐translationally modified proteins such as the Ser139‐phosphorylated histone H2AX and Lys9‐methylated histone H3, with less dependence on the LPxTG motif. Our study validates the chemical modification of substrates as an effective means of augmenting the synthetic capability of existing enzymatic methods. [ABSTRACT FROM AUTHOR]

The regioselective ring‐opening of 1,2‐ and 1,3‐sulfamidates with fluorine anion is reported. Direct construction of monofluoro‐substituted amines and amino acid derivatives using inexpensive and easily available potassium fluoride (KF). The monofluorination process only needs 35 minutes under heating, which will be an attractive route for the synthesis of the PET fluorine‐18 radiotracer. The application of the product can be extended to the construction of fluorinated polypeptides after simple deprotection treatment. [ABSTRACT FROM AUTHOR]

Thalassospiramides A and B are immunosuppressant cyclic lipopeptides first reported from the marine α-proteobacterium Thalassospira sp. CNJ-328. We describe here the discovery and characterization of an extended family of 14 new analogues from four Tistrella and Thalassospira isolates. These potent calpain 1 protease inhibitors belong to six structure classes in which the length and composition of the acylpeptide side chain varies extensively. Genomic sequence analysis of the thalassospiramide-producing microbes revealed related, genus-specific biosynthetic loci encoding hybrid nonribosomal peptide synthetase/polyketide synthases consistent with thalassospiramide assembly. The bioinformatics analysis of the gene clusters suggests that structural diversity, which ranges from the 803.4 Da thalassospiramide C to the 1291.7 Da thalassospiramide F, results from a complex sequence of reactions involving amino acid substrate channeling and enzymatic multimodule skipping and iteration. Preliminary biochemical analysis of the N- terminal nonribosomal peptide synthetase module from the Thalassospira TtcA megasynthase supports a biosynthetic model in which in cis amino acid activation competes with in trans activation to increase the range of amino acid substrates incorporated at the N terminus. [ABSTRACT FROM AUTHOR]

Albino tea plants are mutants that grow albino young leaves owing to lack of chlorophylls under certain environmental conditions. There are two types of albino tea plants grown in production, i.e., light- and temperature-sensitive albino tea cultivars. The former grows albino leaves in yellow color under intensive sunlight conditions and the later grows albino leaves with white mesophyll and greenish vein as the environmental temperature is below 20 °C. Both albino teas attract great attention because of their high levels of amino acids and the "umami" taste. There have been many studies focusing on the temperature-sensitive albino tea plants, whereas little attention has been given to the light-sensitive albino tea cultivars. The characteristics of the albino tea cultivars and the mechanism underlying them were reviewed in the present article based on the published literatures, including chemical compositions, morphological characteristics, and molecular genetic mechanism. [ABSTRACT FROM AUTHOR]

Gonadotropin-releasing hormone (GnRH) is the central regulator of reproduction in vertebrates. GnRHs have recently been identified in protochordates and retain the conserved N- and C-terminal domains involved in receptor binding and activation. GnRHs of the jawed vertebrates have a central achiral amino acid (glycine) that favors a type II′ β-turn such that the N- and C-terminal domains are closely apposed in binding the GnRH receptor. However, protochordate GnRHs have a chiral amino acid in this position, suggesting that they bind their receptors in a more extended form. We demonstrate here that a protochordate GnRH receptor does not distinguish GnRHs with achiral or chiral amino acids, whereas GnRH receptors of jawed vertebrates are highly selective for GnRHs with the central achiral glycine. The poor activity of the protochordate GnRH was increased »10-fold at vertebrate receptors by replacement of the chiral amino acid with glycine or a D-amino acid, which favor the type II′ β-turn. Structural analysis of the GnRHs using ion mobility-mass spectrometry and molecular modeling showed a greater propensity for a type II′ β-turn in GnRHs with glycine or a D-amino acid, which correlates with binding affinity at vertebrate receptors. These findings indicate that the substitution of glycine for a chiral amino acid in GnRH during evolution allows a more constrained conformation for receptor binding and that this subtle single amino acid substitution in a site remote from the ligand functional domains has marked effects on its structure and activity. [ABSTRACT FROM AUTHOR]