In1 order to increase the expression level of gene for recombinant phytase in Pichia pastoris, a synthetic sequence of the phyOp-mod gene, which encodes phytase from Obesumbacterium proteus, has been designed and optimized by its codon composition. The GC content was adjusted to 48.33%, and AT-rich segments were eliminated. The main characteristics for the purified enzyme are established. The optimal pH and temperature values for РhyOp phytase functioning prove to be 4.0 and 50°C, respectively. The specific activity, Michaelis constant (Km), and maximal rate of reaction (Vmax) with sodium phytate as a substrate are 1452 U/mg, 0.31 mM, and 823 U/mg, respectively. It is shown that optimization of the codon composition increased the expression of the target product gene. The recombinant phytase designated as PhyOp demonstrated great potential for application as a feed additive due to its relatively high specific activity and good kinetic characteristics.