Enzymes insulin

Enzymes are highly specific catalysts in biological systems. They are proteins that consist of many amino acids coupled to each other by peptide bonds. The rather small enzyme insulin, for example, consists of 51 amino acids. The chain of amino... 

Hydroxy-3-methylglutaryl (HMG)-CoA reductase on the smooth endoplasmic reticulum (SER) is the rate-limiting enzyme. Insulin acth"ates the enzyme (dephosphorylation), and glucagon inhibits it. Mevalonate is the product, and the statin drugs competitively inhibit the enzyme. Cholesterol represses the expression o the HMG-CoA reductase gene and also increases degradation of the enzyme. 

Proteins are the third major class of biomolecules. The word protein comes from the Greek word proteios meaning primary. Protein is the primary material composing cells. Fifty percent of the human body is composed of proteins, and it is estimated that roughly 100,000 different proteins are found in humans. Protein is a major component of structural and connective tissue found in skin, ligaments, bones, muscles, and tendons. Digestive enzymes, insulin, and other hormones are proteins. 

In addition to its effects on the activity of existing enzymes, insulin also regulates the expression of as many as 150 genes, including some related to fuel metabolism... 

Human insulin Chromosome ene removed wilh human by enzymes insulin gene... 

The kidney plays a major role in the clearance of insulin from the systemic circulation, removing approximately 50% of endogenous insulin and a greater proportion of insulin administered to diabetic patients (19). Insulin is filtered at the glomerulus and reabsorbed by proximal tubule cells, where it is degraded by proteolytic enzymes. Insulin requirements are markedly reduced in diabetic patients with impaired renal function. Imipenem and perhaps other... 

Keywords Amyloid precursor protein Apolipoprotein E p-amyloid peptide Beta-amyloid precursor protein converting enzyme Insulin degrading enzyme Neurofibrillary tangle Oxidative damage Presenilin-1... 

Stimulates gallbladder contraction and intestinal motility stimulates secretion of pancreatic enzymes, insulin, glucagon, and pancreatic polypeptides has a role in indicating satiety the C-terminal 8-amino acid peptide GGR-8 retains full activity... 

Phosphoenolpyruvate carboxykinase (PEPCK) - This enzyme has no known allosteric regulators. The enzyme is controlled by hormonal regulation of its synthesis. The hormone, glucagon, activates transcription of the structural gene for the enzyme. Insulin, on the other hand, inhibits transcription of the gene. 

Glucagon exerts its ejfects on cells by binding to a receptor on the cell surface, which stimulates the synthesis of the intracellular second messenger, cyclic adenosine monophosphate (cAMP) (Fig. 26.3). cAMP activates protein kinase A, which phosphorylates key regulatory enzymes, activating some and inhibiting others. Changes of cAMP levels also induce or repress the synthesis of a number of enzymes. Insulin promotes the dephosphorylation of these key enzymes. 

Liver Insulin increases the storage of glucose as glycogen in the liver. This involves the insertion of additional GLUT 2 glucose transport molecules in cell walls, increased synthesis of the enzymes pyruvate kinase, phosphofructokinase. and glucokina.se, and the suppression of several other enzymes. Insulin also decreases protein catabolism. 

The pancreas serves several functions which includes the secretion of the enzyme insulin which controls blood glucose metabolism level. Over a million diabetic persons must take Insulin injections on a regular basis (l). The metabolism control by this method is erratic and several research groups have been experimenting with polymeric infusion pumps in order to control the insulin level (and thus the glucose level) more... 

At least seven hormones, including ACTH, epinephrine, and glucagon, attack the adipose tissue and lead to the breakdown of triglycerides to yield free glycerol and fatty acids. After each hormone has attached to its own specific receptor, they all act through a common mechanism—the stimulation of adenyl cyclase— with proportionate elaboration of cAMP. The cAMP activates the lipase, possibly by phosphorylation of the enzyme. Insulin and certain prostaglandins inhibit lipolysis and decrease the level of cAMP in the cell. In contrast, theophylline and caffeine inhibit the phosphodiesterase and thereby increase lipolysis in the fat cells (see Fig. 8-35). 

The years that have passed since Sanger determined the structure of insulin have seen refinements m technique while retaining the same overall strategy Enzyme cat alyzed hydrolysis to convert a large peptide to smaller fragments remains an important... 

Disulfides. As shown in Figure 4, the and h-chains of insulin are connected by two disulfide bridges and there is an intrachain cycHc disulfide link on the -chain (see Insulin and other antidiabetic drugs). Vasopressin [9034-50-8] and oxytocin [50-56-6] also contain disulfide links (48). Oxidation of thiols to disulfides and reduction of the latter back to thiols are quite common and important in biological systems, eg, cysteine to cystine or reduced Hpoic acid to oxidized Hpoic acid. Many enzymes depend on free SH groups for activation—deactivation reactions. The oxidation—reduction of glutathione (Glu-Cys-Gly) depends on the sulfhydryl group from cysteine. 

Enzyme immunosensors are employed for the determination of Hepatitis B surface antigen, IgG, alpha-fetoprotein, estradiol, theophylline, insulin [9004-10-8] and alburnin (69,70). However, these immunosensors generally have slow response times and slow reversibiUty (57). 

It appears that chromium(III) is an essential trace element in mammalian metabolism and, together with insulin, is responsible for the clearance of glucose from the blood-stream. Tungsten too has been found to have a role in some enzymes converting CO2 into formic acid but, from the point of view of biological activity, the focus of interest in this group is unquestionably on molybdenum. 

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