THE EFFECT OF VITAMIN-C ON N-ACETYLTRANSFERASE ACTIVITY IN KLEBSIELLA-PNEUMONIAE

This study was designed to assess the effect of vitamin C on arylamine N-acetyltransferase (NAT) activity in Klebsiella pneumoniae by using HPLC to measure the acetylation of 2-aminofluorene (2-AF) with and wit hout vitamin C. Two assay systems were performed, one with intact bact erial cell suspensions, the other with S-9 fractions (9000 g supernata nt). It was found that vitamin C promoted NAT activity in K. pneumonia e in a dose-dependent manner in both systems. 4 and 8 mM vitamin C wer e selected for further studies in S-9 fractions and intact cell system s, respectively. Through a 4-hr time course study, vitamin C promoted the N-acetylation of 2-AF in both assay systems, but, the longer the r eaction time lasted, the lower the promotion rate. In the kinetic stud ies, vitamin C increased the value of K-m from 0.42 +/- 0.03 mM to 2.4 3 +/- 0.87 mM in S-9 fraction assays and from 0.54 +/- 0.03 mM to 0.85 +/- 0.18 mM in intact cell assays. Vitamin C also increased the appar ent V-max values from 3.52 +/- 0.08 to 39.66 +/- 9.81 nmol/min/mg prot ein in S-9 fraction assays, and from 1.28 +/- 0.06 to 4.88 +/- 0.87 nm ol/min/10(10) CFU in intact cell assays, for acetylation of 2-AF. In t he presence of vitamin C, the NAT activity was increased from 0.58 +/- 0.06 to 1.34 +/- 0.02 nmol/min/mg protein in S-9 fractions, and from 0.18 +/- 0.02 to 0.40 +/- 0.02 nmol/min/10(10) CFU in intact cells, fo r acetylation of 2-AF. From the present study, it is concluded that vi tamin C does promote the N-acetylation of 2-AF in K. pneumoniae. This is a first report suggesting that oral vitamin C may be involved in mo difying the mutagenicity/carcinogenicity of ingested arylamines throug h enhancing the NAT activity of human enteric bacteria. This interacti on should be pursued in future in vivo studies. (C) 1997 Elsevier Scie nce Ltd. All rights reserved.