Sandbox 54321

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Function

Lisinopril is an orally active angiotensin-converting enzyme inhibitor, or ACE inhibitor, used primarily to lower blood pressure. Lisinopril works by antagonizing the effect of the RAAS, which is a homeostatic mechanism for regulating hemodynamics, water and electrolyte balance. During sympathetic stimulation or when renal blood pressure or blood flow is reduced, renin is released from the granular cells of the juxtaglomerular apparatus in the kidneys. In the blood stream, renin cleaves circulating angiotensinogen to ATI, which is subsequently cleaved to ATII by ACE. ATII increases blood pressure using a number of mechanisms. ACE inhibitors inhibit the rapid conversion of ATI to ATII, and also antagonize RAAS-induced increases in blood pressure. ACE (also known as kininase II) is also involved in the enzymatic deactivation of bradykinin, which is a vasodilator. When the deactivation of bradykinin is inhibited, bradykinin levels are increased and this can further sustain the effects of lisinopril by causing increased vasodilation and decreased blood pressure.^[3] Overall, lisinopril inhibits the substances in the body that cause blood vessels to tighten, and as a result lisinopril relaxes the blood vessels and therefore lowers blood pressure and increases the supply of blood and oxygen to the heart.^[4]

Structure

is a synthetic angiotensin-converting enzyme inhibitor (ACE inhibitors) with molecular formula of C21+H31+N3+O5, empirical formula of C21+H31+N3+O5*2H2O, and average molecular weight of 405.495 g/mol. It is primarily used for the treatment of hypertension^[5]. Lisinopril is typically in the trans isometric form because it has a lower steric repulsion between the hydroxyl and carboxyl groups than the cis conformation and is biologically active in this form ^[6].Lisinopril has a benzene ring and from there it has a 4-carbon amide chain where it branches of into a carboxylic acid group one way and a secondary amide group the other way which connects to the rest of the molecule. From the secondary amide, the molecule branches into a 5-carbon amine with a primary amide at the end. The other branch from the secondary amide has a ketone bonded to a nitrogen in a 4-carbon ring. From this carbon ring, there is a carboxylic acid group.

Relevance

Structural highlights

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Mechanism

Lisinopril is a drug used mainly to treat hypertension but also to reduce the risk of long-term damage and death in patients suffering from heart failure. Lisinopril controls blood pressure by inhibiting the angiotensin converting enzyme (ACE). By inhibiting ACE, it inevitably prevents the body from synthesizing angiotensin II. Without the surplus of angiotensin II being made, the blood pressure in the body lowers due to the increase in the ratio of vasodilating angiotensin I to vasoconstricting angiotensin II (Helen, 2016). There are two mechanisms that inhibit ACE proteins due to the different locations they are in the body. Coded by the same gene, the somatic and testis ACE enzymes are closely similar though display some differences. The testes ACE protein consists of two domains which include their own individual HEXXH zinc binding motif which forms many ligands that catalyze the hydrolysis of many mechanisms. In respect to Lisinopril, the zinc ions are involved with the hydrolysis of angiotensin I where the His-Leu dipeptide residues are cleaved at the C domain which restricts access to the active site. The binding position in the C domains actually control the conversion of angiotensin, therefore when Lisinopril binds to ACE, which becomes distorted and curved. The curved and helical structure is known as tACE. This helical structure is formed via the chloride ions near the active site which begin substrate hydrolysis in the C domain. Lisinopril is known to bind to the individual HEXXH zinc binding motif in the lysine side chain and in addition the extended phenyl group near the active site (Natesh, 2003).