ABSTRACT

I. INTRODUCTION A. Traditional Approach for Analysis of Phosphoproteins For expression of their biological activity, bioactive peptides are synthesized in the cell body via a long chain of events starting with transcription, from the peptide gene, of mRNA that encodes the precursor protein. The nascent precursor protein then undergoes proteolytic cleavage and posttranslational modifications during its transport through the endoplasmic reticulum, Golgi complex, and secretary vesicles to produce a bioactive peptide. The important posttranslational modifications include proteolytic cleavage, acylation (acetyl, formyl, and myristyl), carboxylation, glycosylation, lipidation, amidation, phosphorylation, and sulfation. The knowledge of this so-called "regulated pathway" for a specific precursor family is of practical significance because the inability of a regulatory mechanism to function normally leads to metabolic aberrations underlying various pathophysiological and clinical manifestations.