Tripetides

Tripetides, more commonly referred to as tripeptides in current biochemistry, are short chains of three amino acids linked together by peptide bonds. As the smallest unit of peptides beyond dipeptides, they are often encountered as intermediates in digestion and protein turnover, and they can also occur as miniature signaling or functional peptides in various organisms. The term tripetide is encountered in older or non-English texts and is largely superseded by tripeptide in modern usage.

Tripetides are classified by their amino acid composition: homotripetides (three of the same amino acid) and heterotripetides (three different amino acids). The sequence determines properties such as charge, hydrophobicity, and receptor affinity. They are formed through condensation reactions between amino acids or longer peptides, typically via enzymes during proteolysis or by chemical synthesis in the laboratory. Tripetides can be hydrolyzed further to dipeptides and amino acids by proteases.

Physiological roles include digestion, where proteases generate tripetides from dietary proteins, and transport, as some tripetides are absorbed via specific peptide transporters in the intestinal lining. Some tripetides also function as signaling molecules, neurotransmitters, or pharmacologically active agents, and they serve as intermediates in metabolic pathways such as the synthesis of larger peptides and proteins. Because of their small size, they are often used as model systems in peptide chemistry and as building blocks for studying protein folding and enzyme specificity.