Abstract: There are disclosed a protein having an amino acid sequence shown in SEQ ID NO:2, or a protein having a glutaminase activity in which one or more amino acids is/are deleted from, substituted by, inserted to or added to the amino acid sequence of the above protein; a gene containing DNA encoding the above protein or a gene which hybridizes with the a complementary sequence of DNA of the above gene under a stringent condition and encodes a protein having a glutaminase activity; a recombinant DNA containing the above gene; a transformant or a transductant containing the above recombinant DNA; and a process for producing glutaminase which comprises culturing the above transformant or the above transductant and collecting glutaminase from a culture medium.