Detection of dipeptidyl peptidase IV in glioma C6 and neuroblastoma SK-N-SH cell lines

Abstract

The dipeptidyl peptidase IV (DPP-IV) activity of the rat glioma cell line C6 and the human neuroblastoma cell line SK-N-SH was investigated. DPP-IV fluorescent substrate was cleaved by both cell lines. The pH reaction optimum determined was typical for DPP-IV described in other cell models. The reaction was inhibited by specific inhibitors diprotins A and B. Enzyme activity was localized, both on the cell surface and intracellularly. Most of the DPP-IV activity was membrane bound. However, soluble intra-cellular activity was found in both cell lines. Secreted activity was not detected in either cell line. In the C6 line, but not in the SK-N-SH line, we demonstrated depression of the ratio of cell surface to total cell DPP-IV activity at higher cell densities, indicating possible enzyme redistribution during cell growth in culture. Identification of DPP-IV activity is the first step in our study of the role of DPP-IV in the neural system.