Analysis of transketolase and identification of an enzyme variant in human leukocytes

Human leukocyte transketolase of fresh cell extracts has been analyzed by isoelectrofocusing on agarose gels (pH 3-10). The enzyme was then transblotted on nitrocellulose and detected with specific anti-transketolase IgG coupled to an avidin/biotin-immunoperoxidase system. Each sample yielded multiple enzyme forms, within a pI range of about 7.4-8.4. Transketolase profile, however, was not identical in all extracts. There are two mainly distinct patterns, showing qualitative and quantitative differences: a standard profile, which is predominant, and a variant, found in three unrelated subjects out of the two hundred and twenty. Standard and variant enzyme have similar Km values for ribose 5-P and xylulose 5-P and the same mobility on SDS-PAGE.