H. Jahansouz, K. B. Mertes, M. Mertes
Jun 1, 1989
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0
Influential Citations
6
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Journal
Bioorganic Chemistry
Abstract
Abstract The hydrolysis of formyl phosphate was studied in unbuffered and buffered solutions. In the absence of buffer the rate constant (8.8 × 10 −3 min −1 at 25°C and pH 7) varies little from about pH 5 to 8 and increases dramatically at low and high pH values. At pH 7 the hydrolysis appears to proceed via two mechanisms, nucleophilic attack on the carbonyl carbon and a mechanism involving PO bond cleavage. This is based on the facts that the reaction proceeds 45% by CO bond cleavage and 55% by PO bond cleavage (shown using H 2 18 O) ; there is a solvent isotope effect of 1.6; the Δ S ‡ (−11.8 e.u.) is intermediate between that expected for a unimolecular and a bimolecular reaction; the reaction rate is affected by organic solvent and buffer. At pH 1 and 11 the mechanism is entirely nucleophilic substitution at the carbonyl since the reaction proceeds 100% by CO cleavage, and the Δ S ‡ (−21.3 and −25.5 e.u.) is that expected for a bimolecular reaction. In the presence of Tris and glycine the formyl phosphate disappearance is accompanied by formylation of the primary amines with a 100% yield in the case of glycine. Imidazole and pyridine also catalyze formyl phosphate breakdown. In the former case the reaction proceeds primarily by CO cleavage, but no formylated product was observed. Differences in the hydrolyses of formyl phosphate and acetyl phosphate are discussed.