Abstract P206: Structural Analysis of Glycosyl Chain at 14th Amino Acid Of Human Angiotensinogen in Plasma

Abstract

The Renin angiotensin system (RAS) is a major regulator of body fluid balance and control of blood pressure. The protease enzyme renin secreted from kidneys cleaves speci[[Unable to Display Character: fi]]cally angiotensinogen (Aogen) circulating in the blood to produce angiotensin I (Ang I). Human Aogen is a heterogeneous glycoprotein constitutively secreted by the liver. In addition, human Aogen contains four putative asparagine-linked glycosylation sites (Asn 14, 137, 271, 295) and contains four cysteines (Cys 18, 138, 232, 308), with Cys18 and Cys138 linked by a disulfide bridge. The glycosyl chains and cysteines position are very important for binding of the renin. Big angiotensin-25 (Bang-25) is a consisting of 25 amino acids with glycosyl chain (14th amino asid) and added cysteine (18th amino acid), which we recently isolated from human urine. To compare glycosyl chain of Bang-25 and Aogen, we analyzed of structure glycosyl chain at position 14th amino acid of human Aogen in plasma. To determine of glycosyl chain at position 14th amino acid, we performed lysyl endopeptidase digestion and reduction on human plasma Aogen. Then, Aogen after digest was purified by reverse-phase high-performance liquid chromatograpy (RP-HPLC), and glycosyl chain structure analyzed by the two-/three-dimensional HPLC mapping method. We show that plasma Aogen has three types of glycosyl chain at position 14th amino acid. One glycosyl chain structure is identical to Bang-25 in urine. N-linked glycosylation on 14th amino acid of Aogen plays an important role about renin reaction. In addition, Bang-25 is rapidly cleaved by chymase to Ang II, but is resistant to cleave by renin. These results suggest that the structure of the glycosyl chain at position 14th amino acid of the human Aogen may be involved in the substrate specificity for renin or chymase.