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Sulfolobus solfataricus is a thermophilic archaebacterium able to grow at 87°C and pH 3.5 on glucose as sole carbon source. The organism metabolizes glucose by two main routes. The first route involves an ATP-dependent phosphorylation to give glucose 6-phosphate, which readily isomerizes to fructose 6-phosphate. In t-he second route, glucose is converted into gluconate by an NAD+-dependent dehydrogenation; gluconate is then dehydrated to 2-keto-3-deoxygluconate, which, in turn, is cleaved to pyruvate and glyceraldehyde. Each metabolic step has been tested in vitro at 70°C on dialysed homogenates or partially purified fractions; minimal requirements of single enzymes have been evaluated. Identification of the intermediates is based on chromatographic, spectroscopic and/or synthetic evidence and on specific enzymic assays. The oxidative breakdown of glucose to pyruvate occurring in S. solfataricus differs from the Entner-Doudoroff pattern in that there is an absence of any phosphorylation step.

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A poly(ADP-ribose) polymerase-like enzyme, detected in a crude homogenate from Sulfolobus solfataricus by means of activity and immunoblot analyses, was purified to electrophoretic homogeneity by a rapid procedure including two sequential affinity chromatographies, on NAD + -agarose and DNA-Sepharose. The latter column selected specifically the poly(ADP-ribosyl)ating enzyme with a 17 % recovery of enzymic activity and a purification of more than 15 000-fold. The molecular mass (54-55 kDa) assessed by SDS\PAGE and immunoblot was definitely lower than that determined for the corresponding eukaryotic protein.The enzyme was proved to be thermophilic, with a temperature optimum of approx. 80 mC, and thermostable, with a half-life of 204 min at 80 mC, in good agreement with the requirements of a

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