The term phytase comprises several different classes of enzymes.

This minireview on phytases’ classification is dedicated to honor Professor I.C. Gunsalus, a great mentor to one of us. Several of the research findings from our laboratory had reached his office in the form of manuscripts as editor of Biochemical Biophysical Research Communications. Professor Gunsalus supported our work by encouraging us to publish in a timely fashion. He leaves a legacy of outstanding research and a willingness to encourage others to conduct innovative work. We thank him for encouraging us to push the boundary of phytase research over the last decade.