title: Subcellular localization of gamma-glutamyltransferase in calf thymocytes.
abstract: The subcellular localization of gamma-glutamyltransferase in calf thymocytes was investigated and compared with that of alkaline phosphodiesterase I, alkaline nitrophenyl phosphatase, succinate-tetrazolium oxidoreductase (succinate-INT reductase) and lactate dehydrogenase after two different methods of cell disruption and differential centrifugation. Most of the activity was recovered in the crude membrane fractions (43.0%), but significant amounts co-pelleted with the large-granule (mitochondria) fractions (31%). The specific activity of the gamma-glutamyltransferase in the purified plasma membrane was 30-50 times that of the enzyme in the cell homogenate and had a similar subcellular distribution to the plasma-membrane markers, alkaline phosphodiesterase I and alkaline nitrophenyl phosphatase. It was concluded that gamma-glutamyltransferase was primary a plasma-membrane-bound enzyme, and that its location in other subcellular fractions was probably due to their contamination with plasma-membrane vesicles.
mesh_terms: D000818:Animals; D002417:Cattle; D002458:Cell Fractionation; D002462:Cell Membrane / Q000201:enzymology; D013347:Subcellular Fractions / Q000201:enzymology; D013950:Thymus Gland / Q000201:enzymology* / Q000648:ultrastructure; D005723:gamma-Glutamyltransferase / Q000378:metabolism*
chemical_list: D005723:gamma-Glutamyltransferase