Abstract: The present invention relates to a thermostable enzyme with a 2.1 Å crystal structure of a propeller type comprising six external blades that encompass the outer boundary of the crystal and six internal calcium-binding sites that are embedded inside the above crystal. Each of the six blades comprises 4 or 5 anti-parallel &bgr;-strands, and the six calcium binding sites consist of 3 high-affinity calcium binding sites and 3 low-affinity binding sites, which are involved in the enzyme's thermostability and catalytic activity, respectively. The above-mentioned Ca2+ binding motifs are expected to be utilized in synthesizing highly thermostable proteins and the elucidation of active sites of an enzyme from a three-dimensional structure can help to design new enzymes having those sites with the aid of recent advanced technology of protein engineering.

Abstract: The strain Bacillus sp. DS11 (KCTC 0231BP) is disclosed and a phytase produced by DS11 having the following characteristics: optimum temperature: 65° C.; optimum pH: 7.0; molecular weight: 43,000 dalton; isoelectric point: 5.6; and a specified N-terminal amino acid sequence. The bacterial strain DS11 or the phytase it produces can be used as an animal feed additive.