Involvement of catalytic amino acid residues in enzyme-catalyzed polymerization for the synthesis of polyesters.
Recently, a variety of aliphatic polyesters have been synthesized using hydrolases such as lipases and PHB depolymerases, and the reaction mechanism for these enzyme-catalyzed polymerization has been discussed. In this paper, we have studied the involvement of the catalytic amino acid residues of the hydrolase in enzyme-catalyzed polymerization with an extracellular PHB depolymerase from Alcaligenes faecalis T1. A wild-type PHB depolymerase and three kinds of site-specific mutants (catalytic amino acids were substituted) were prepared and their polymerization activities for the ring-opening polymerization of (R)-beta-butyrolactone (BL) were compared. BL was polymerized at 80 degrees C in bulk by the wild-type enzyme to yield polymers consisting of cyclic and linear structures in a high monomer conversion. In contrast, none of the mutant enzymes showed obvious polymerization activity. These results have clearly demonstrated that the catalytic triad is indeed responsible for the enzyme-catalyzed polymerization of BL.
Suzuki
Y
Y
Polymer Chemistry Laboratory, RIKEN Institute, 2-1, Hirosawa, Wako-shi, Saitama 351-0198, Japan.
Taguchi
S
S
Saito
T
T
Toshima
K
K
Matsumura
S
S
Doi
Y
Y
D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000737:chemistry*; D000421:Alcaligenes / Q000201:enzymology* / Q000235:genetics; D002265:Carboxylic Ester Hydrolases / Q000737:chemistry* / Q000235:genetics; D002384:Catalysis; D016297:Mutagenesis, Site-Directed; D011091:Polyesters / Q000737:chemistry*
D011091:Polyesters; C013426:beta-butyrolactone; D002265:Carboxylic Ester Hydrolases; C022417:poly-beta-hydroxybutyrate depolymerase; D015107:4-Butyrolactone