Hyperproinsulinaemia in obese fat/fat mice associated with a carboxypeptidase E mutation which reduces enzyme activity

Nat Genet. 1995 Jun;10(2):135-42. doi: 10.1038/ng0695-135.


Mice homozygous for the fat mutation develop obesity and hyperglycaemia that can be suppressed by treatment with exogenous insulin. The fat mutation maps to mouse chromosome 8, very close to the gene for carboxypeptidase E (Cpe), which encodes an enzyme (CPE) that processes prohormone intermediates such as proinsulin. We now demonstrate a defect in proinsulin processing associated with the virtual absence of CPE activity in extracts of fat/fat pancreatic islets and pituitaries. A single Ser202Pro mutation distinguishes the mutant Cpe allele, and abolishes enzymatic activity in vitro. Thus, the fat mutation represents the first demonstration of an obesity-diabetes syndrome elicited by a genetic defect in a prohormone processing pathway.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Carboxypeptidase B
  • Carboxypeptidase H
  • Carboxypeptidases / genetics*
  • Carboxypeptidases / metabolism
  • Cattle
  • Chromosome Mapping
  • Conserved Sequence
  • Enzyme Activation
  • Female
  • Islets of Langerhans / enzymology
  • Islets of Langerhans / ultrastructure
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Inbred NOD
  • Mice, Obese
  • Mice, SCID
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Mutation*
  • Pituitary Gland / enzymology
  • Proinsulin / blood*
  • Proinsulin / metabolism
  • Rats
  • Sequence Alignment
  • Transfection


  • Proinsulin
  • Carboxypeptidases
  • Carboxypeptidase H
  • Carboxypeptidase B