Biochemical characterization of an organic solvent-tolerant glycosyltransferase from Bacillus licheniformis PI15 with potential application for raspberry ketone glycoside production.

Raspberry ketone is a primary aroma component of the red raspberry. The glycosylation of this compound is a potential approach used to improve its pharmaceutical properties. In this work, raspberry ketone glycosides are produced in bacteria for the first time. Bacillus licheniformis PI15, an organic solvent-tolerant glycosyltransferase-producing strain, was isolated from chemically polluted soil. The cloning and heterologous expression of a glycosyltransferase, which was designated PI-GT1, in Escherichia coli BL21 resulted in the expression of an active and soluble protein that accounted for 15% of the total cell protein content. Purified PI-GT1 was highly active and stable over a broad pH range (6.0-10.0) and showed excellent pH stability. PI-GT1 maintained almost 60% of its maximal activity after 3 H of incubation at 20-40 °C and demonstrated optimal activity at 30 °C. Additionally, PI-GT1 displayed high stability and activity in the presence of hydrophilic solvents with log P ≤ -0.2 and retained more than 80% of its activity after 3 H of treatment. Supplementation with 10% DMSO markedly improved the glycosylation of raspberry ketone, resulting in a value 26 times higher than that in aqueous solution. The organic solvent-tolerant PI-GT1 may have potential uses in industrial chemical and pharmaceutical synthesis applications.

rac-Methyl 2-(2-formyl-4-nitro-phen-oxy)hexa-noate.

In the racemic title compound, C(14)H(17)NO(6), the plane of the ester group of the methyl hexa-noate side chain makes a dihedral angle of 80.0 (2)° with the benzene ring, while the nitro group is approximately coplanar with the benzene ring [dihedral angle = 10.3 (2)°]. In the crystal, mol-ecules form weak aromatic C-H⋯O(nitro) hydrogen-bonding inter-actions, giving inversion dimers [graph set R(2) (2)(8)].

[2-(1H-Indol-4-yl)eth-yl]dipropyl-amine.

In the title compound, C(16)H(24)N(2), the aliphatic amine substituent is rotated almost orthogonally [C-C-C-C torsion angle = 75.7 (3)°] out of the plane of the indole unit. The amine N atom has a pyramidal configuration deviating by 0.380 (3) Šfrom the plane of the adjacent C atoms. All of the aliphatic groups are in extended transoid conformations. In the crystal, mol-ecules form chains along the a axis via N-H⋯N hydrogen bonds.

N-Cyclo-hexyl-N-{[3-(4,6-dimeth-oxy-pyrimidin-2-yl-oxy)pyridin-2-yl]meth-yl}4,6-dimeth-oxy-pyrimidin-2-amine.

In the title compound, C(24)H(30)N(6)O(5), the cyclo-hexyl ring adopts a chair conformation, while the remainder of the mol-ecule adopts a U-shape. The dihedral angles between the pyridine ring and the pendant pyrimidine rings are 69.04 (12) and 75.99 (9)°. The two pyrimidine rings, however, are nearly parallel to one another, with a dihedral angle of 8.56 (15)° between them. They are also involved in an intra-molecular π-π stacking inter-action with a distance of 3.6627 (18) Šbetween the ring centroids. In the crystal, C-H⋯O contacts link the mol-ecules into chains along the b axis.

2-[(4,6-Dimeth-oxy-pyrimidin-2-yl)-oxy]benzaldehyde.

In the title compound, C(13)H(12)N(2)O(4), the dihedral angle between the benzene and pyrimidine rings is 55.57 (13)°. The carbonyl group and the two methoxyl groups are approximately coplanar with the benzene ring and pyrimidine ring; the C-C-C-O, C-O-C-N and C-O-C-C torsion angles being -6.1 (5), -4.8 (4) and 179.9 (3)°, respectively. In the crystal, mol-ecules are linked via C-H⋯O inter-actions, forming chains propagating along [110].

N-(2,6-Dichloro-phen-yl)-5-methyl-1,2-oxazole-4-carboxamide monohydrate.

In the title compound, C(11)H(8)Cl(2)N(2)O(2)·H(2)O, the dihedral angle between the benzene and isoxazole rings is 59.10 (7)°. In the crystal, the components are linked by N-H⋯O and O-H⋯O hydrogen bonds into a three-dimensional network. The crystal structure is further stabilized by π-π stacking inter-actions [centroid-centroid distance = 3.804 (2) Å].