1-O-Acetyl-β-d-galactopyranose: a novel substrate for the transglycosylation reaction catalyzed by the β-galactosidase from Penicillium sp.

Abstract 1- O -Acetyl-β- d -galactopyranose (AcGal), a new substrate for β-galactosidase, was synthesized in a stereoselective manner by the trichloroacetimidate procedure. Kinetic parameters ( K M and k cat ) for the hydrolysis of 1- O -acetyl-β- d -galactopyranose catalyzed by the β- d -galactosidase from Penicillium sp. were compared with similar characteristics for a number of natural and synthetic substrates. The value for k cat in the hydrolysis of AcGal was three orders of magnitude greater than for other known substrates. The β-galactosidase hydrolyzes AcGal with retention of anomeric configuration. The transglycosylation activity of the β- d -galactosidase in the reaction of AcGal and methyl β- d -galactopyranoside ( 1 ) as substrates was investigated by 1 H NMR spectroscopy and HPLC techniques. The transglycosylation product using AcGal as a substrate was β- d -galactopyranosyl-(1→6)-1- O -acetyl-β- d -galactopyranose (with a yield of ∼70%). In the case of 1 as a substrate, the main transglycosylation product was methyl β- d -galactopyranosyl-(1→6)-β- d -galactopyranoside. Methyl β- d -galactopyranosyl-(1→3)-β- d -galactopyranoside was found to be minor product in the latter reaction.