Catechol-O-methyltransferase (COMT1) catalyzes the transfer of a methyl group from S-adenosylmethionine (SAM) to various catechol substrates. COMTs play vital roles in physiological processes in animals, plants, and fungi, as well as bacteria, and have essential application values in industry. spCOMT is a probable COMT from Schizosaccharomyces pombe. It has an extraordinary intracellular distribution different from other homologs and would thus be predicted to perform a distinct physiological function. In this report, recombinant spCOMT was purified and kinetically characterized for the first time. The enzymology assays indicate that spCOMT is a metal-dependent enzyme and belongs to class I OMTs. In addition, the crystal structures of apo-spCOMT and SAM-complexed spCOMT were also presented, revealing that spCOMT possesses a conserved SAM-binding site and Mg2+ pocket, but a distinct substrate pocket was not present in homologs. The mutagenesis ITC analysis revealed the SAM recognition characteristics of spCOMT. Based on all of the above findings, we speculated about the putative substrates' characteristics and the substrate recognition mechanisms of spCOMT. This work will help in elucidating the physiological functions of spCOMT in S. pombe. (c) 2018 IUBMB Life, 71(3):330-339, 2019