An isolated and purified human skeletal muscle-specific ubiquitin-conjugating enzyme comprising the amino acid sequence shown in SEQ ID NO: 22 is disclosed. The use of the genes make it possible to detect the expression of the same in various tissues, analyze their structures and functions, and produce the human proteins encoded by the genes by the technology of genetic engineering. Through these, it becomes possible to analyze the corresponding expression products, elucidate the pathology of diseases associated with the genes, for example hereditary diseases and cancer, and diagnose and treat such diseases.