Altered isoelectric focusing of α2-macroglobulin from plasma of patients with diabetes mellitus

Stephen Back, Mara Lorenzi, Jack A. Alhadeff

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

Plasma from both type I and type II patients with diabetes mellitus displayed elevated α2-macroglobulin trypsin-binding activity relative to normals. Column isoelectric focusing indicated that the average isoelectric point (pI) of the major form of crude α2-macroglobulin was 6.6, 5.9, and 6.2 for normal, type I and type II subjects, respectively. Focused crude diabetic α2-macroglobulin displayed significantly less recovered trypsin-binding activity relative to controls, particularly above a pI value of 6.0. Following preincubation with trypsin, the crude diabetic α2-macroglobulin displayed a single isoelectric form (pI value of 5.3-5.5) and a substantial increase in recovered activity which were both comparable to normal α2-macroglobulin. Purified α2-macroglobulin from both normal and diabetic subjects displayed similar focusing profiles having a distribution of three forms with a pI value of 5.3-5.4 for the principal form. Trypsin-preincubated samples of purified α2-macroglobulin displayed a single form with a pI value of 5.5-6.0. Preincubation of purified normal or diabetic α2-macroglobulin with a plasma preparation devoid of α2-macroglobulin from normal or diabetic plasma resulted in significantly lowered recovery of activity. All of the above studies suggest that the altered focusing properties observed for crude diabetic α2-macroglobulin are due to components of the plasma rather than to α2-macroglobulin itself.

Original languageEnglish (US)
Pages (from-to)21-29
Number of pages9
JournalClinica Chimica Acta
Volume150
Issue number1
DOIs
StatePublished - Jul 30 1985
Externally publishedYes

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Keywords

  • Diabetes mellitus
  • Isoelectric focusing
  • α-Macroglobulin

ASJC Scopus subject areas

  • Biochemistry
  • Clinical Biochemistry

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