Abstract
Arabinogalactan proteins (AGPs) were the extracellular proteoglycans associated with the plasma membrane, and their functions have been implicated in diverse developmental roles including differentiation, cell-cell recognition, and embryogenesis. AGPs are characterized by large amounts of carbohydrate components rich in galactose and protein components containing hydroxyproline. In spite of the importance of AGPs, study of enzymes which attack to carbohydrate moiety of AGPs is limited. Recently, we succeeded in the cloning a beta-1,3-galactanase gene from Phanerochaete chrysosporium for the first time. In the present study, we searched the database of the Arabidopsis thaliana genome based on the sequence, and found two homologous regions. The amino acid sequences deduced from the nucleotide sequences suggest that the genes encode membrane enzymes belonging to glycoside hydrolase family 43. The genes were successfully expressed in the methylotrophic yeast Pichia pastoris, and both recombinant proteins hydrolyzed beta-1,3-galactan. The result indicates that the genes encode to beta-1,3-galactanase.
