RT Journal Article SR Electronic(1) A1 de Forchetti, Silvia R. Milrad A1 Cazzulo, J. J.YR 1976 T1 Some Properties of the Pyruvate Carboxylase from Pseudomonas fluorescens JF Microbiology, VO 93 IS 1 SP 75 OP 81 DO https://doi.org/10.1099/00221287-93-1-75 PB Microbiology Society, SN 1465-2080, AB Summary: The pyruvate carboxylase of Pseudonomas fluorescens was purified 160-fold from cells grown on glucose at 20 °C. The activity of this purified enzyme was not affected by acetyl-coenzyme A or l-aspartate, but was strongly inhibited by ADP, which was competitive towards ATP. Pyruvate gave a broken double reciprocal plot, from which two apparent Km values could be determined, namely 0·08 and 0·21 mm, from the lower and the higher concentration ranges, respectively. The apparent K m for HCO− 3 at pH 6·9, in the presence of the manganese ATP ion (MnATP2−), was 3·1 mm. The enzyme reaction had an optimum pH value of 7·1 or 9·0, depending on the use of MnATP2− or MgATP2−, respectively, as substrate. Free Mg2+ was an activator at pH values below 9·0. The enzyme was strongly activated by monovalent cations; NH+ 4 and K+ were the better activators, with apparent Ka values of 0·7 and 1·6 mm, respectively. Partially purified enzymes from cells grown on glucose at 1 or 20 °C had the same properties, including the thermal stability. In both cases 50% of the enzyme activity was lost after preincubation for 10 min at 46 °C. The molecular weight was estimated to be about 300000 daltons by gel filtration on Sephadex G-200. The regulatory properties and molecular weight are thus similar to those determined for the pyruvate carboxylases from Pseudomonas citronellolis and Azotobacter vinelandii. , UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-93-1-75