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 β - 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 &# 39 ; s thermostability and catalytic activity , respectively . the above - mentioned ca 2 + 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 .