International Journal of Applied Science and Engineering 2005. 3, 1: 61-68 Int. J. Appl. Sci. Eng., 200 5. 3, 1 61 Isolation and Characterization of Mandibular Organ – Inhibiting Hormone from the Eyestalks of Freshwater Crab, Oziotelphusa Senex Senex G. Purna Chandra Nagaraju * , G. LakshmiVara Prasad, and P. Sreenivasula Reddy Department of Biotechnology, Sri Venkateswara University, Tirupati – 517 502, India Abstract: Eyestalk neuropeptides play an important role in regulating wide variety of physio- logical processes in crustaceans. The neuropeptides belonging to the crustacean hyperglycemic hormone (CHH) family, influence the secretion of ecdysteroids and methyl farnesoate (MF) and in turn regulate molting and reproduction. Using MF secretion by Mandibular organ (MO) as bioassay two peptides with distinctive Mandibular organ-inhibiting hormone (MO-IH) activity was identified. Among these one peptide possesses hyperglycemic activity. Keywords: eyestalk neuropeptides; mandibular organ; Mandibular organ-inhibiting hormone. * Corresponding author: e-mail: raju@cc.ncue.edu.tw Accepted for Publication: Feb. 22, 2005 © 2005 Chaoyang University of Technology, ISSN 1727-2394 1. Introduction During the last half-century, extensive studies on the crustacean hyperglycemic hormone (CHH) family peptides have vali- dated their roles in the control of several physiological functions and further disclosed the details of biochemical and molecular mechanisms of their action [1]. The CHH family peptides are secreted by the eyestalk of sinus gland (SG) [2], which in turn controls the reproduction, molting, and metabolism. Sinus gland the neurohemal organ of crusta- ceans is located between the medulla externa and the medulla interna on the dorsolateral surface of the eyestalk ganglia in the crab Oziotelphusa senex senex [2]. Methyl farnesoate (MF), the unepoxidated form of Juvenile hormone III of insects, is synthesized and released by the mandibular organ (MO) in decapod crustaceans and ap- pears to regulate many aspects of physiology, including the stimulation of reproduction, molting and morphogenesis [2]. Recent stud- ies have focused on the biosynthesis of MF and its regulation, because the role of MF in crustaceans remains unclear [3]. Mandibular organ-inhibiting hormone (MO-IH) is synthesized and secreted by the X-organ-sinus gland complex of the eyestalk. Unfortunately, it has been difficult to develop a sensitive assay, such as a radioimmuno as- say, for measuring circulating levels of MO-IH. It has been demonstrated that SG extracts and purified MO-IH directly inhibit the secretion of methyl farnesoate from man- dibular organ in vitro [4], suggesting that MO-IH is physiologically important in the regulation of the crustacean molt and repro- duction. This hypothesis is additionally sup- ported by data showing that purified MO-IH delays molting and reproduction [5-7]. The purpose of these studies was to isolate and characterize a peptide with MO-IH activity