Elementary plant Biochemistry and Biotechnology (2+1)

iii. Derived proteins

• These are proteins derived by partial to complete hydrolysis from the simple or conjugated proteins by the action of acids, alkalies or enzymes. They include two types of derivatives, primary-derived proteins and secondary-derived proteins
 
Primary-derived proteins

• These protein derivatives are formed by processes causing only slight changes in the protein molecule and its properties
• There is little or no hydrolytic cleavage of peptide bonds.

Proteans

• Proteans are insoluble products formed by the action of water, dilute acids and enzymes. These are particularly formed from globulins but are insoluble in dilute salt solutions.e.g., myosan from myosin, fibrin from fibrinogen

Metaproteins

• These are formed by the action of acids and alkalies upon protein. They are insoluble in neutral solvents. Coagulated proteins
• Coagulated proteins are insoluble products formed by the action of heat or alcohol on natural proteins,e.g., cooked meat and cooked albumin

Secondary-derived proteins

• These proteins are formed in the progressive hydrolytic cleavage of the peptide bonds of protein molecule. They are roughly grouped into proteoses, peptones and peptides according to average molecular weight. Proteoses are hydrolytic products of proteins, which are soluble in water and are not coagulated by heat. Peptones are hydrolytic products, which have simpler structure than proteoses


• They are soluble in water and are not coagulated by heat. Peptides are composed of relatively few amino acids. They are water-soluble and not coagulated by heat. The complete hydrolytic decomposition of the natural protein molecule into amino acids generally progresses through successive stages as follows
Protein Protean →Metaprotein
Proteoses →Peptones →Peptides →amino acids