Principles of Protein Structure - H. Schultze 1982

Covalent Protein Structure
Enzyme-Controlled Modifications of the Main Chain
Specific Cleavage of the Polypeptide Chain

Specific proteolysis is a convenient process for The formation of complex protein structures. In many cases, Proteins are modified by the Cleavage of one or more peptide bonds. The terms "Limited proteolysis" or "specific proteolysis" (Table 4.2) are used to describe this type of enzyme-catalyzed reactions, which play a dominant role in numerous physiological processes [137–139]. Well-known Examples of specific polypeptide cleavage include the activation of digestive enzyme precursors, morphogenetic processes in bacterial Viruses, and the cascade processes of Blood Coagulation and Complement action [138, 140]. It has recently been shown that post-translational cleavage mechanisms also occur during the formation of such diverse proteins as Insulin, Collagen, and virus-specific proteins. In addition, highly specific proteolytic cleavage of Enzymes is important for the inactivation and activation of specific intracellular enzymes (Table 4.2).

Class="center">Table 4.2 Aspects of specific proteolysis

Biological process

Example of limited proteolysis

Functional aspects

Formation of virus-specific proteins in animal viruses [163, 164]

Poliovirus protein precursor → poliovirus proteins

Adaptation of viruses to the Specific features of Protein Synthesis in animal Cells

Morphogenesis of Viral Particles [140]

Two independent sub-structures of virus 14 → formation from two sub-structures

Cleavage of the polypeptide chain creates new binding sites; the irreversibility of proteolytic reactions facilitates the ordering of viral particle assemblies

Formation of Connective Tissue [125; 127, 131]

Procollagen with attached fragments at the N- and C-termini → collagen triple helix + large Polypeptides

Cleavage of fragments from collagen after its Processing and transport as a soluble precursor

Digestion [138]

Trypsinogen —Trypsin + small peptide

Activation of the protease at the appropriate time and physiologically appropriate Location

Blood coagulation [148]

Inactive coagulation factor A → active coagulation factor A+peptide; then A activates inactive

coagulation factor B, etc.

Protective trigger system of many proenzymes; Amplification

of the response using an enzyme cascade; control at each level of the cascade

Complement action [147]

Complement factor → one or two active complement proteins

Protective trigger system consisting of at least 18 Serum proteins; a series of specific proteolytic reactions restricts complement action in time and space. Soluble proteins bind to the membrane

Toxin action [165]

Diphtheria toxin → enzymatically active fragment + penetrating fragment

Protease of the affected Cell releases the lethal enzymatically active fragment of the toxin

Protein degradation [154–156, 166]

Serine dehydratase (apoenzyme) → large fragment + small peptide

Protein inactivation and breakdown are often initiated by a single specific proteolytic step

Hormone formation [167]

Proglucagon Glucagon + octapeptide

Proinsulin → insulin + C-peptide

The extrapeptide is the C-terminal part of the prohormone

Cleavage of the properly folded proenzyme automatically leads to the functioning protein

Protein secretion [153]

Protrypsinogen → trypsinogen + hydrophobic peptide

Removal of the signal sequence capable of transmitting information to the environment

A process opposite to specific proteolysis, namely protein elongation [141], is also known. An example of the attachment of the C-terminus of one protein to the N-terminus of another is the assembly process of bacterial viruses [142].



Last update: 06/08/2026

Editorial and Educational Adaptation: This material has been compiled based on the primary/original source text. The project team performed an editorial review, corrected technical inaccuracies, structured sections, and adapted the content for an educational format.

What was processed:

  • elimination of formatting defects (OCR errors, structural breaks, corrupted characters);
  • editorial organization of content;
  • standardization of terminology in accordance with academic sources;
  • verification of factual statements against the original source text.

All mentions of the author, publication year, and origin of the primary text have been preserved in accordance with the source.