Comparative characterisation of poly(ADP-ribose) polymerase-1 from two mammalian species with different life span

DNA damage induced in higher eukaryotes by alkylating agents, oxidants or i onising radiation triggers the synthesis of protein-conjugated poly(ADP-rib ose) catalysed by poly(ADP-ribose) polymerase-1 (PARP-1). Previously, cellu lar poly(ADP-ribosyl)ation capacity has been shown to correlate positively with the life span of mammalian species [Proc. Natl. Acad. Sci. USA 89 (199 2) 11 759-11 763]. Here, we have tested whether this correlation results fr om differences in kinetic parameters of the enzymatic activity of PARP-1. W e therefore compared recombinant enzymes, expressed in a baculovirus system , from rat and man as two mammalian species with extremely divergent life s pan. In standard activity assays performed in the presence of histones as p oly(ADP-ribose) accepters both enzymes showed saturation kinetics with [NAD (+)]. The kinetic parameters (k(cat), k(m) and k(cat)/k(m)) of the two enzy mes were not significantly different. However, in assays assessing the auto -poly(ADP-ribosyl)ation reaction, both enzymes displayed second-order kinet ics with respect to [PARP-1], and up to twofold higher specific activity wa s observed for human versus rat PARP-1. We conclude that the correlation of poly(ADP-ribosyl)ation capacity with life span is not reflected in the kin etic parameters, but that subtle differences in primary structure of PARP-1 from mammalian species of different longevity may control the extent of th e automodification reaction. (C) 2000 Elsevier Science Inc. All rights rese rved.