Purification and Some Properties of GTP Cyclohydrolase I from Spinach Leaves

Abstract

GTP cyclohydrolase I (EC 3.5.4.16) has been purified for the first time from a higher plant, spinach leaves. The purified preparation appeared to be homogeneous on polyacrylamide gel electrophoresis. The molecular weight of this enzyme was estimated at 135, 000 by gel filtration and the subunit molecular weight was estimated at 35, 000 by SDS-PAGE. The latter method also suggested that this enzyme was composed of four identical subunits. The enzyme was stable to heat treatment at 50°C for 10 min, and the activity was maintained for at least six months when stored at -30°C. The enzyme had an optimum pH of around 8.0 in Tris buffer. The Hill coefficient of the enzyme was calculated to be 2.2. The pI of the enzyme was measured as 5.1 by chromatofocusing.