Crystallization and preliminary X-ray diffraction analysis of thermophilic imidase from pig liver.

Imidase is an enzyme, also known as dihydropyrimidinase (EC 3.5.2.2), hydantoinase, dihydropyrimidine hydrase or dihydropyrimidine amidohydrolase, that catalyzes the reversible hydrolysis of 5,6-dihydrouracil to 3-ureidopropionate and many other imides. Substrate specificity, metal content and amino-acid sequence all differ significantly between bacterial and mammalian imide-hydrolyzing enzymes. In this study, a thermophilic imidase was isolated from pig liver and crystallized. Two kinds of imidase crystals were grown by the hanging-drop vapour-diffusion method using polyethylene glycol MME 5000 and 2-propanol as precipitants. One belongs to the triclinic P(1) space group, with unit-cell parameters a = 96.35, b = 96.87, c = 154.87 A, alpha = 82.10, beta = 72.54, gamma = 77.19 degrees, and the other belongs to the orthorhombic C222(1) space group, with unit-cell parameters a = 113.92, b = 157.22, c = 156.21 A.