BACKGROUND/AIMS: NAD glycohydrolase (NADase) is abundantly expressed in the liver. This expression is prominent in Kupffer cells. Since it was recognized that reticulendothelial function is impaired in liver cirrhosis, we assessed how these enzyme activities were altered in patients with liver cirrhosis. METHODS: Serum samples were obtained from 61 patients with liver cirrhosis (according to the criteria of Child-Pugh 15 were classified A, 24 were classified B, and 22 were classified C) and 16 healthy subjects. NADase activities were measured fluorometrically with [adenine-14C] NAD. The reaction mixture contained [adenine-14C] NAD and enzyme (patient serum). The reaction was stopped after a 30 to 480 min incubation by the addition of 50 L of 25% trichloroacetic acid. RESULTS: Serum NADase activities in 61 patients with liver cirrhosis were significantly lower than those in healthy subjects (33+/-14 vs. 55.6+/-13 p<0.001). Serum NADase activities in severe cirrhotic patients were significantly lower than those in mild to moderate cirrhotic patients (criteria of Child-Pugh, A: 40.6+/-6.4 vs. B: 38.6+/-13 vs. C: 21.8+/-14, p<0.001). NADase activities were correlated to prothrombin time (r = 0.69), and Apo A1 (r = 0.58) that were useful in identifying high-risk subjects for severe liver disease, but not asparate aminotransferase (AST) and alanine aminotransferase (ALT). Also, NADase activities reciprocally correlated with PGAA index (r = -0.78), Child-Pugh's score (r = -0.48), and serum alpha-2-macroglobulin (r = -0.72). CONCLUSIONS: NADase activities could be used as a single diagnostic marker for liver cirrhosis in addition to the Child-Pugh's score and PGAA index.
Alanine Transaminase ; Apolipoprotein A-I ; Humans ; Kupffer Cells ; Liver Cirrhosis* ; Liver Diseases ; Liver* ; NAD* ; NAD+ Nucleosidase* ; Prothrombin Time ; Trichloroacetic Acid

ADP-ribosyltransferase (ADPRT) catalyzes the reaction in which the ADP-ribose moiety of beta-NAD+ is transferred to specific amino acid residues in target proteins. The ADPRT of Mycobacterium smegmatis has been known to inactivate rifampin through ADP-ribosylation. However, the enzymatic characteristics and functions of the enzyme have not been elucidated yet. In this study, the ADPRT-glutathione S-transferase (GST) fusion protein was expressed in Escherichia coli and enzymatic characteristics of the fusion protein were investigated. ADPRT-GST fusion protein was an ADPribosyltransferase that had no NAD glycohydrolase activity. ADPRT-GST fusion protein showed no self-inactivation phenomenon that is a universal nature for all NAD glycohydrolases and is important in regulating its activity. ADPRT activity of the enzyme was decreased by novobiocin and isonicotinic acid hydrazide. These results suggest that Mycobacterium smegmatis ADPRT could be regulated by a different way from other NADases and involved in bacterial physiological process through a post-translational modification of cytosolic proteins.
Adenosine Diphosphate Ribose ; ADP Ribose Transferases* ; Cytosol ; Escherichia coli ; Isoniazid ; Mycobacterium smegmatis* ; Mycobacterium* ; NAD+ Nucleosidase ; Novobiocin ; Physiological Processes ; Protein Processing, Post-Translational ; Rifampin