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. Author manuscript; available in PMC: 2024 Feb 29.
Published in final edited form as: Life Metab. 2023 Dec 8;3(1):load048. doi: 10.1093/lifemeta/load048

Figure 2.

Figure 2

Tissue-specific contrast of size and structure. Evolutionary processes build proteins and synthesize peptides with specific characteristic features fine-tuned to make them bioactive, versatile, and dynamically regulated. (a and b) Splicing of apolipoprotein generates two specific proteins, ApoB-100 of 500 kDa in the liver (a) and ApoB-48 of 240 kDa in the intestine (b). (c and d) CCK, a proteolytically processed peptide hormone composed of 8 amino acids, acts as a neurotransmitter in the brain (c). In contrast, in the gastrointestinal tract, the size of CCK varies from 31–58 amino acids and it functions as a digestive peptide hormone (d). (e) The enzyme prohormone convertase 1 (PC1) serially cleaves the prohormone, procholecystokinin (proCCK), into peptides of different size.