The Crystal and Molecular Structure of Vitamin B 6 Derivatives. I. Pyridoxal Phosphate Hydrate and Pyridoxal Phosphate Methyl Hemiacetal
1973; Oxford University Press; Volume: 46; Issue: 3 Linguagem: Inglês
10.1246/bcsj.46.863
ISSN1348-0634
Autores Tópico(s)Enzyme Production and Characterization
ResumoPyridoxal phosphate hydrate (PLPHYD) was crystallized from an aqueous solution in the form of monoclinic needles; space group P21⁄c with a=10.503, b=13.608, c=7.488 Å, β=93.71° and four molecules in the unit cell. Prism-shaped crystal of pyridoxal phosphate methyl hemiacetal (PLPMHA) was obtained by dissolving the pyridoxal phosphate hydrate crystals into 90% methanol; space group P\barl, with cell dimensions, a=9.42, b=10.61, c=6.20 Å, α=105.6°, β=95.7°, and γ=99.7°, and two molecules per cell. Intensity data were collected on an automated diffractometer for PLPHYD and photographically for PLPMHA. Crystal structures have been determined by the symbolic addition method. Refinements were done by the block-diagonal least-squares procedures, the final R value being 0.093 for PLPHYD and 0.112 for PLPMHA. The free aldehyde group of pyridoxal phosphate interacts with water molecule to form gem-diol in the crystalline state of PLPHYD and the gem-diol group of PLPHYD with methanol to form methyl hemiacetal. One of the two hydrogen atoms on a phosphate group is liberated and protonated to the pyridine ring nitrogen atom, resulting in the zwitterionic structure for both PLPHYD and PLPMHA molecules. All hydrogen bonds in PLPHYD are intermolecular ones, but in PLPMHA there is one OH–O intramolecular hydrogen bond.
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