ABSTRACT
This chapter examines the regulation of pro-opiomelanocortin (POMC) and α-melanocyte-stimulating hormone (MSH) biosynthesis at these different levels in intermediate lobe. Several mechanisms may exist for the regulation of synthesis of POMC-derived peptides. These include regulation at the transcriptional level; at the post-transcriptional level; translational level, and post-translational level. During black-background adaptation of the amphibian, the melanophore index of the skin increased to 5 as compared to white-background-adapted animals, which had punctuate melanocytes and a melanophore index of 1. The enzyme, named pro-opiomelanocortin-converting enzyme (PCE), has been characterized as an aspartyl protease. It has an acidic pH optimum and is a 70,000 mol. wt. glycoprotein. PCE is highly specific for paired basic residues. The sequence of the mouse, human, bovine, and rat POMC genes have been characterized. The mouse genome contains two POMC-related gene sequences; α-POMC and β-POMC genes which are located in different chromosomes.
