Traducir Para Comprender

TRADUCIR para comprender:

Insulin

Insulin is a peptide hormone that functions in lowering blood glucose levels. Insulin has several activities that accomplish this goal, summarized below:

1. Insulin inhibits transcription of the enzyme phosphoenolpyruvate carboxykinase (PEPCK). PEPCK is a key enzyme in gluconeogenesis and transcription is the primary means of regulating it. By inhibiting PEPCK transcription, insulin can depress glucose production tremendously. (Conversely, the hormone glucagon, which increases blood glucose levels, stimulates PEPCK transcription.)

2. Insulin stimulates translocation of the glucose transporter protein from cytosol to the cell surface. Glucose transport protein carries out the facilitated transport of glucose.

3. Insulin stimulates phosphatase activity which removes phosphates from molecules activated by the kinase cascade. Thus, insulin opposes the effects of glucagon and epinephrine.

Insulin also stimulates fatty acid biosynthesis as follows:

1. Insulin favors entry of glucose into cells, which, in turn, favors production of NADPH via entry of glucose-6-phosphate into the pentose phosphate pathway.

2. Insulin activates the pyruvate dehydrogenase complex, which favors production of acetyl-CoA.

3. Insulin tends to reverse the effects of the kinase cascade, and stimulates dephosphorylation of acetyl-CoA carboxylase, which favors polymerization of the enzyme in an active form.

Glucagon

Glucagon is a peptide hormone involved in increasing blood levels of glucose.

1. Glucagon acts to stimulate production of cAMP inside of cells. It does this by binding to a specific receptor that, via interaction with a cell membrane G protein, stimulates the activity of the enzyme responsible for making cAMP, adenylate cyclase. cAMP acts as a "second messenger," conveying the signal from outside the cell to the inside and initiating the cell's response. Pathways affected by cAMP include glycogen metabolism, glycolysis, fatty acid biosynthesis.

2. Glucagon stimulates transcription of the enzyme phosphoenolpyruvate carboxykinase (PEPCK). PEPCK is a key enzyme in gluconeogenesis and transcription is the primary means of regulating it. By stimulating PEPCK transcription, glucagon can favor gluconeogenesis over glycolysis. (Conversely, the hormone insulin, which decreases blood glucose levels, stimulates PEPCK transcription.)

3. Glucagon represses synthesis of pyruvate kinase, the last enzyme in the glycolytic pathway. This to has the effect of favoring gluconeogenesis over glycolysis.

Note that transcription regulation mechanisms are relatively long-term effects (hours to days). When glucose levels need to be increased rapidly (in an emergency, for example), other mechanisms, such as stimulation of glycogen breakdown, must be employed. In this regard, glucagon differs from epinephrine. Both glucagon and epinephrine act to stimulate production of cAMP which stimulates glucose production, but epinephrine has no long term effects, as does glucagon.

insulina

La insulina es una hormona peptídica que funciona en la reducción de los niveles de glucosa en sangre . La insulina tiene varias actividades que logran este objetivo , que se resumen a continuación:

1 . La insulina inhibe la transcripción de la enzima fosfoenolpiruvato

...