Background Diabetics lack the protein insulin, which is produced by the pancreat

Question

Background Diabetics lack the protein insulin, which is produced by the pancreatic -cells of the islets of Langerhans. Insulin stimulates uptake of glucose from the blood into the tissues. Diabetes is treated by replacing the missing insulin. Human insulin is produced industrially by recombinant bacteria, but before this method was available, animal insulin was used instead. Insulin consists of two polypeptide chains, an A chain and a B chain, joined together by disulfide bonds. The smaller of the two chains is referred to as the A chain and is 21 amino acids long in humans. The second chain is referred to as the B chain and is 30 amino acids long in humans. Insulin from various animals is similar to, but not identical to human insulin, as illustrated in Table 1. A schematic diagram of the structure of insulin is shown in Figure 1 Table 1: Variation in positions A8, A9, A10, B1, B2, B27 and B30 of insulin. (All other amino acids are the same.) Species A10 B27 B30 A8 Thr Ala Thr Thr Thr Thr A9 Ser Ser Ser Gl Ser Ser AsnThr Asn B1 B2 VaThrThr Va Th Ala Val Va Th Ala Val human Phe CoW Val Phe Phe Phe Phe Ala Ala Thr Ala pig horse rabbit Thr Ser Val ThAla 0 chicken 1S Ala Ser Ala duck Glu ro Ala Ser Thr

Explanation / Answer

1, Ans-

                         Pig insulin is the best sources of insulin to be used for treating diabetics because of single one amino acid variation in B30. Cow insulin has two variations in A8 and B30 positions, and one difference in A10 position.
                        Pig and cow are the good sources to replace human insulin because of easily available their products from slaughterhouses, whereas horse, dog, and rabbit are not. Chicken and duck insulin are not good enough because there have seven and six amino acid variations as compared to human insulin.
2.Ans-
                    The pI values for all of the animal insulins would be the same to human insulin except chicken and duck because the amino acid changes all the neutral amino acids that involved. The pI valued of chicken and duck insulin are the exception because chicken insulin would be more basic whereas duck would be more acidic.

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