Expression and Characterization of Hyperthermostable Exopolygalacturonase RmGH28 from Rhodothermus marinus.

The gene RmGH28 from the organism Rhodothermus marinus, a putative glycosyl hydrolase family 28 polygalacturonase, was expressed in Escherichia coli and biochemically characterized. The gene was found to encode an exopolygalacturonase termed RmGH28, with galacturonic acid monomer and the polymer substrate (n-1) as the products released when acting on de-esterified polygalacturonic acid from citrus pectin. The enzyme at 25 °C had k ∼6 s when acting on polygalacturonic acid, with K ∼0.