Soluble, prolonged-acting insulin derivatives. I. Degree of protraction and crystallizability of insulins substituted in the termini of the B-chain.
Hydrophilic insulins, more positively charged than human insulin at neutral pH, have been prepared by substitution with basic amino acids at the termini of the B-chain and by blocking the C-terminal carboxyl group of the B-chain. The isoelectric pH of the insulin is thereby moved from 5.4 towards physiological levels. Slightly acid solutions of derivatives, in which charge has been added in the C-terminus of the B-chain, have a prolonged action in vivo, in particular if the carboxyl group is blocked. It is found that the prolonged-acting hydrophilic insulins crystallize instantly when the pH is adjusted to 7. The prolonged action is ascribed to this readiness to crystallization combined with a low solubility, which may be further decreased by increased concentration of zinc ions. Hydrophobic insulins have a prolonged action independent of the site of substitution even if the derivative is soluble at physiological pH. Some derivatives were prepared from porcine insulin by tryptic transpeptidation. N-terminal B-chain substituted insulins were prepared by alkylation of a biosynthetic single-chain insulin precursor, followed by tryptic transpeptidation rendering the double chain insulin derivative. The observed blood glucose lowering in the rabbits implies that neither N- nor C-terminal B-chain substitution results in substantial deterioration of biological potency. An index for the degree of protraction based on the blood glucose data is used to compare the insulins.
Markussen
J
J
Novo Research Institute, Bagsvaerd, Denmark.
Hougaard
P
P
Ribel
U
U
Sørensen
A R
AR
Sørensen
E
E
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D003460:Crystallization; D003692:Delayed-Action Preparations; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000235:genetics; D008297:Male; D051379:Mice; D015202:Protein Engineering; D011817:Rabbits; D012995:Solubility; D013552:Swine
D001786:Blood Glucose; D003692:Delayed-Action Preparations; D007328:Insulin