_____________________________________________________________________________________________________ *Corresponding author: E-mail: omihandd@gmail.com; International Journal of Biochemistry Research & Review 15(1): 1-8, 2016; Article no.IJBCRR.30399 ISSN: 2231-086X, NLM ID: 101654445 SCIENCEDOMAIN international www.sciencedomain.org Heavy Metals Effect on the Activity and Kinetics of Peroxidase Enzyme in Crude Extracts of Rosmarinus officinalis and Eruca sativa Omar M. Atrooz 1* , Manar A. Al-Btoush 1 and Ibrahim M. Al-Rawashdeh 2 1 Department of Biology, Mutah University, P.O.Box 7, Mutah, Jordan. 2 Department of Biological Science, Al-Hussein Bin Talal University, P.O.Box 20, Maan, Jordan. Authors’ contributions This work was carried out in collaboration between all authors. Author OMA designed the study, wrote the protocol and supervised the work. Author MAAB carried out all laboratories work and performed the statistical analysis. Author IMAR wrote the first draft of the manuscript. Authors OMA and IMAR managed the literature searches and edited the manuscript. All authors read and approved the final manuscript. Article Information DOI: 10.9734/IJBCRR/2016/30399 Editor(s): (1) Hector M. Mora Montes, Department of Biology, University of Guanajuato, Mexico. Reviewers: (1) Flávio Henrique Silveira Rabêlo, University of São Paulo, Brazil. (2) Naeem Khan, Kohat University of Science and Technology, Pakistan. Complete Peer review History: http://www.sciencedomain.org/review-history/17466 Received 7 th November 2016 Accepted 30 th November 2016 Published 7 th January 2017 ABSTRACT The catalytic activities and kinetic parameters of the enzyme peroxidase (POX), extracted from two plant species namely Rosmarinus officinalis and Eruca sativa, were investigated in the presence and absence of various heavy metals. The activation effects of heavy metals Co 2+ , Fe 3+ and Pb 2+ have performed a noncompetitive inhibition on the enzyme activity in the crude extract of Eruca sativa. In contrast, Cd 2+ , Ni + and Cu 2+ have an uncompetitive inhibition for the two selected plants. Furthermore, Fe 3+ , Al 3+ , Pb 2+ and Mo 2+ were found to be acted as noncompetitive inhibitors on the enzyme activity in the crude extract of Rosmarinus officinalis. Presence of heavy metals altered the enzyme activity by acting as uncompetitive or noncompetitive inhibitors depending on the type of heavy metals. Keywords: Relative activities; uncompetitive inhibition; noncompetitive inhibition. Original Research Article