Genetic and protein engineering of diagnostic enzymes, cholesterol oxidaseand xylitol oxidase

For a long time, clinical diagnosis has been made mainly using chemical met hods. Recently, several excellent substrate-specific enzymes have been deve loped and these enzymes are used as diagnostic catalysts. Using enzymes, it is possible to assay for a specific substance from specimens of serum or u rine without the need for isolation of the substance which simplifies the p rocess and shortens the assay time. Furthermore, the use of enzymatic assay methods for diagnosis has been facilitated by the developments in genetic engineering which made it possible to overproduce enzymes inexpensively. He re, we review the diagnostic enzymes, cholesterol oxidase and xylitol oxida se, which were successfully overproduced in our laboratory. In particular, the catalytic activity and pH and thermal stabilities of cholesterol oxidas e were improved.