Asymmetric acyloin condensation catalysed by phenylpyruvate decarboxylase.Part 2: Substrate specificity and purification of the enzyme

Phenylpyruvate decarboxylase from Achromobacter eurydice was used to cataly se the asymmetric acyloin condensation of phenylpyruvate 1 with Various ald ehydes 2 to produce optically active acyloins PhCH2COCH(OH)R 3. The specifi c activity of the phenylpyruvate decarboxylase enzyme was increased by a fa ctor of 332 after its purification. The molecular weight of the purified en zyme was shown to be 150 kDa by gel filtration chromatography, while SDS ge l electrophoresis showed two sub-units with molecular weights of 90 and 40 kDa. The acyloin condensation yield decreased with increasing chain length for straight chain aliphatic aldehydes from 76% for acetaldehyde to 24% for valeraldehyde. The e.e.s of the acyloin products were 87-98%. Low yields o f acyloin products were obtained with chloroacetaldehyde (13%) and glycoald ehyde (16%). Indole-3-pyruvate was a substrate of the enzyme and provided a cyloin condensation product 3-hydroxy-1-(3-indolyl)-2-butanone 5 with aceta ldehyde in 19% yield, while benzoylformate was not a substrate for the enzy me. (C) 2001 Elsevier Science Ltd. All rights reserved.