An insulin that is produced in the pancreas and involved in regulating the metabolism of carbohydrates (particularly glucose) and fats. Commonly thought of as a protein, it consists of two peptide chains, one containing 21 amino acid residues and the other containing 30; the chains are joined together by 2 disulfide bonds. Recombinant insulin is identical to human insulin, but is synthesised by inserting the human insulin gene into <em>E. coli</em>, which then produces insulin for human use. It is used in the treatment of type I and type II diabetes.