Protease have evolved multiple times, and different classes of protease can perform same reactions by different catalytic mechanism. Protease can be found in animals, plants, bacteria, archea and viruses. The impact factor of journal provides quantitative assessment tool for grading, evaluating, sorting and comparing journals of similar kind. It reflects the average number of citations to recent articles published in science and social science journals. The impact factor of a journal is evaluated by dividing the number of current year citations to the source items published in that journal during the previous two years.