Cis-prenyltransferases are enzymes responsible for the biosynthesis of glycosyl carrier lipids, natural rubber, and some secondary metabolites. Certain organisms, including some archaeal species, possess multiple genes encoding cis-prenyltransferase homologs, and the physiological roles of these seemingly-redundant genes are often obscure. Cis-prenyltransferases usually form homomeric complexes, but recent reports have demonstrated that certain eukaryotic enzymes are heteromeric protein complexes consisting of two homologous subunits. In this study, three cis-prenyltransferase homolog proteins, MM_0014, MM_0618, and MM_1083, from the methanogenic archaeon Methanosarcina mazei are overexpressed in Escherichia coli and partially purified for functional characterization. Coexistence of MM_0618 and MM_1083 exhibits prenyltransferase activity, while each of them alone has almost no activity. The chain-lengths of the products of this heteromeric enzyme are in good agreement with those of glycosyl carrier lipids extracted from M. mazei, which are likely di- and tetra-hydrogenated decaprenyl phosphates, suggesting that the MM_0618/MM_1083 heteromer is involved in glycosyl carrier lipid biosynthesis. MM_0014 acts as a typical homomeric cis-prenyltransferase and produces shorter products. Copyright © 2019 Elsevier Inc. All rights reserved.