Enables histone methyltransferase activity (H4-K20 specific). Involved in several processes, including histone H4-K20 trimethylation; negative regulation of gene expression, epigenetic; and negative regulation of transposition. Is expressed in several structures, including alimentary system; brain; heart; skeletal musculature; and spleen. Orthologous to human SMYD5 (SMYD family member 5). [provided by Alliance of Genome Resources, Apr 2022]