Engineered rat insulin I analogue having a B16 Tyr/Asp replacement exhibits unchanged susceptibility to cleavage by insulin proteinase.
An analogue of rat insulin I was produced by oligonucleotide-directed mutagenesis of a cloned rat preproinsulin I cDNA, followed by expression of a resulting mutant gene in Escherichia coli K-12 and proteolytic cleavage of mutant proinsulin isolated from this bacterium. The Tyr-to-Asp replacement at residue B16 in the insulin analogue had been expected to diminish the rate of cleavage of the molecule by the enzyme insulin proteinase, since the bond TyrB16-LeuB17, invariant in all mammalian species, had been proposed by other authors as one of the early, major sites of proteolytic attack. In the event the substitution had no measurable effect on the rate of degradation by insulin proteinase. Thus we find no support in these experiments for the hypothesis that the site in question is of primary importance in the degradation of rat insulin I by the enzyme.
Varley
J M
JM
Department of Medical Biochemistry, University of Geneva, Switzerland.
Davies
J G
JG
Shire
D
D
Offord
R E
RE
Timmis
K N
KN
D000818:Animals; D004252:DNA Mutational Analysis; D005818:Genetic Engineering; D007328:Insulin / Q000235:genetics* / Q000378:metabolism; D007339:Insulysin / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship
D007328:Insulin; D011994:Recombinant Proteins; D010447:Peptide Hydrolases; D007339:Insulysin