title: Gamma-glutamyltransferase fractions in human plasma and bile: characteristic and biogenesis.
abstract: Total plasma gamma-glutamyltransferase (GGT) activity is a sensitive, non-specific marker of liver dysfunction. Four GGT fractions (b-, m-, s-, f-GGT) were described in plasma and their differential specificity in the diagnosis of liver diseases was suggested. Nevertheless fractional GGT properties have not been investigated yet. The aim of this study was to characterize the molecular nature of fractional GGT in both human plasma and bile. Plasma was obtained from healthy volunteers; whereas bile was collected from patients undergoing liver transplantation. Molecular weight (MW), density, distribution by centrifugal sedimentation and sensitivity to both detergent (deoxycholic acid) and protease (papain) were evaluated. A partial purification of b-GGT was obtained by ultracentrifugation. Plasma b-GGT fraction showed a MW of 2000 kDa and a density between 1.063-1.210 g/ml. Detergent converted b-GGT into s-GGT, whereas papain alone did not produce any effect. Plasma m-GGT and s-GGT showed a MW of 1,000 and 200 kDa, and densities between 1.006-1.063 g/ml and 1.063-1.210 g/ml respectively. Both fractions were unaffected by deoxycholic acid, while GGT activity was recovered into f-GGT peak after papain treatment. Plasma f-GGT showed a MW of 70 kDa and a density higher than 1.21 g/ml. We identified only two chromatographic peaks, in bile, showing similar characteristics as plasma b- and f-GGT fractions. These evidences, together with centrifugal sedimentation properties and immunogold electronic microscopy data, indicate that b-GGT is constituted of membrane microvesicles in both bile and plasma, m-GGT and s-GGT might be constituted of bile-acid micelles, while f-GGT represents the free-soluble form of the enzyme.
authors.affiliation: Department of Biology, University of Pisa, Pisa, Italy.
authors.forename: Irene
authors.initials: I
authors.lastname: Fornaciari
authors.affiliation: Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy.
authors.forename: Vanna
authors.initials: V
authors.lastname: Fierabracci
authors.affiliation: Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Corti
authors.affiliation: Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy.
authors.forename: Hassan
authors.initials: H
authors.lastname: Aziz Elawadi
authors.affiliation: Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy.
authors.forename: Evelina
authors.initials: E
authors.lastname: Lorenzini
authors.affiliation: Cardiology and Cardiovascular Medicine Division, Fondazione Toscana G. Monasterio - CNR, Pisa, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Emdin
authors.affiliation: Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy ; Cardiology and Cardiovascular Medicine Division, Fondazione Toscana G. Monasterio - CNR, Pisa, Italy.
authors.forename: Aldo
authors.initials: A
authors.lastname: Paolicchi
authors.affiliation: Cardiology and Cardiovascular Medicine Division, Fondazione Toscana G. Monasterio - CNR, Pisa, Italy ; Life Science Institute, Scuola Superiore Sant'Anna, Pisa, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Franzini
mesh_terms: D001646:Bile / Q000737:chemistry*; D002784:Cholesterol / Q000097:blood; D003840:Deoxycholic Acid / Q000737:chemistry; D003902:Detergents / Q000737:chemistry; D055354:Exosomes; D006801:Humans; D007150:Immunohistochemistry; D008074:Lipoproteins / Q000097:blood; D008107:Liver Diseases / Q000097:blood / Q000378:metabolism; D017093:Liver Failure / Q000378:metabolism; D008970:Molecular Weight; D010206:Papain / Q000737:chemistry; D010447:Peptide Hydrolases / Q000737:chemistry; D014461:Ultracentrifugation; D005723:gamma-Glutamyltransferase / Q000097:blood* / Q000737:chemistry*
chemical_list: D003902:Detergents; D008074:Lipoproteins; D003840:Deoxycholic Acid; D002784:Cholesterol; D005723:gamma-Glutamyltransferase; C554782:gamma-glutamyltransferase, human; D010447:Peptide Hydrolases; D010206:Papain