This study is the first report on the effectiveness and specificity of alpha-acarviosinyl-(1 -> 4)-alpha-D-glucopyranosyl-(1 -> 6)-D-glucopyranosylidene-spiro-thiohydantoin (PTS-G-TH) inhibitor on the 2-chloro-4-nitropllenyl-4-O-beta-D-galactopyranosyl-maltoside (GalG(2)CNP) and amylose hydrolysis catalysed by human salivary alpha-amylase (HSA). Synthesis of PTS-G-TH was carried out by transglycosylation using acarbose as donor and glucopyranosylidene-spiro-thiohydantoin (G-TH) as acceptor. This new compound was found to be a much more efficient HSA inhibitor than G-TH. The inhibition is a mixed-noncompetitive type on both substrates and only one molecule of inhibitor binds to the enzyme. Kinetic constants calculated from secondary plots are in ,micromolar range. Values of K-EI and K-ESI are very similar in the presence of GalG(2)CNP substrate; 0.19 and 0.24 mu M, respectively. Significant difference can be found for K-EI and K-ESI using amylose as substrate; 8.45 and 0.5 mu M, respectively. These values indicate that inhibition is rather uncompetitive than competitive related to amylose hydrolysis. (c) 2005 Elsevier Inc. All rights reserved.