THE 28K PROTEIN IN URINARY-BLADDER, SQUAMOUS METAPLASIA AND URINE IS TRIOSEPHOSPHATE ISOMERASE

Objectives: The objective of this study was to establish the identity of a protein found:in high concentrations in squamous metaplasia of th e bladder. Design and Methods: The protein was isolated and subjected to a series of physical, chemical, and catalytic studies. Results: In the normal urothelium the protein was confined to a juxtanuclear patte rn on the luminal side of the umbrella cells; in squamous metaplasia a nd squamous cell carcinoma the protein was increased and exhibited a m ore diffuse intracellular distribution. The protein was found to be id entical to triosephosphate isomerase (EC 5.3.1.1; TPI) with respect to its immunological properties, native and subunit molecular weights, e lectrophoretic mobility, catalytic activity, and amino acid sequence. Conclusions: While the basis for the altered distribution of TPI remai ns to be established, the increased amounts of the protein in urine or bladder tissue may be indicative of squamous metaplasia, squamous cel l carcinoma, or other bladder injuries.