Preproinsulin

Preproinsulin is the primary translational product of the INS gene. It is a peptide that is 110 amino acids in length. Preproinsulin is a proinsulin molecule with a signal peptide attached to its N-terminus.

Ribosomes feed the growing amino acid chain (preproinsulin) directly into the ER where the signal peptide (red) is immediately cleaved off by the signal peptidase (red triangle) to yield proinsulin. This is later processed further to mature and active insulin. Cell components and proteins in this image are not to scale.

Insulin synthesis pathway

Preproinsulin is a biologically inactive precursor to the biologically active endocrine hormone insulin. Preproinsulin is converted into proinsulin by signal peptidases, which remove its signal peptide from its N-terminus. Finally, proinsulin is converted into the bioactive hormone insulin by removal of the C-peptide.

Almost no preproinsulin exists in the cell, because removal of the signal peptide is not a separate step, but rather is closely linked to translocation of the protein into the endoplasmic reticulum (ER). For the same reason, preproinsulin is rarely used medicinally, unlike insulin, the mature product, and proinsulin, a stable ER intermediate.

gollark: Ah, there we go.
gollark: ÆÆÆÆÆÆÆÆÆÆÆÆÆÆÆÆÆÆÆÆÆÆÆÆÆÆÆÆ not even reinstalling the python extension worked?
gollark: Even if I'm painlessly killed, this would actually significantly harm osmarks.net development objectives, so it's objectively bad.
gollark: Apioformic things.
gollark: You are ASSUMING things.

See also
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.