THE AREA OF THE MAIN SUBSTRATE CHANNEL IS HIGHLY CONSERVED AMONG ALL TRUE CATALASES

Catalases are protective enzymes that occur in almost all aerobically metabolising organisms. According to the analysed sequence homology th ey can be divided into three subgroups: true catalases, catalase-perox idases and manganese catalases. Our study was focused on the first sub group representing tetrameric molecules with four prosthetic heme grou ps. The area of the main substrate channel delineates one of the most important structural motifs of the beta-barrel domain of each catalase subunit. As described in this paper, it is extremely highly conserved among ail sequenced catalases from ail living kingdoms. Obviously, it is an absolute requirement for all true catalases. This structure app ears essential for the rapid diffusion of the peroxidic substrate from tile molecular surface to the active centre, and for substrate bindin g to the heme iron; and, by hydrogen bonding, to the essential histidi ne (His70 in catalase A from Saccharomyces cerevisiae).