Abstract: Novel proteins which belong to the papain family and are cysteine proteinase enzymes (the cysteine proteinase enzymes are expected to be involved in the turnover of intracellular proteins, antigen presentation, prohormone activation, bone remodeling, etc. and to play important roles in a variety of pathological conditions such as Alzheimer's disease, pulmonary emphysema, rheumatoid arthritis, muscular dystrophy, osteoporosis, neurodegenerative disease, and cancer invasion and metastasis), together with genes encoding the proteins and antibodies against the proteins, can be conveniently used in elucidating the function of a cysteine proteinase involved in various diseases and disorders, especially cancers, thereby not only disclosing critical mechanism leading to such diseases and disorders but also researching and developing therapy and therapeutic drugs thereagainst.