PMID: 9069Aug 1, 1976

Isolation and characterization of human plasma alpha 1-proteinase inhibitor and a conformational study of its interaction with proteinases

The Biochemical Journal
J SaklatvalaD D White


1. alpha 1-Proteinase inhibitor was isolated from human plasma by a five-step procedure. Isoelectric focusing showed that six components focused between pH4.85 and 4.95. 2. The mol.wt. of the inhibitor was 52000 by sedimentation equilibrium and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. The amino acid and carbohydrate compositions of the inhibitor were also determined. 3. The far-u.v.c.d. (circular-dichroism) spectrum indicated that the inhibitor had about 36% alpha-helical content. 4. The loss of proteinase-inhibitory activity when the inhibitor was exposed to pH values less than 5.0 or greater than 10.5 was accompanied by small changes in the far-u.v.c.d. spectrum and large changes in the near-u.v.c.d. spectrum. The change at alkaline pH was associated with ionization of tyrosine residues. 5. Interaction of inhibitor with chymotrypsin caused perturbation of the c.d. spectrum and this was used to follow the interaction and show a 1:1 stoicheiometry. 6. C.d., electrophoresis and isoelectric focusing showed that the inhibitor-enzyme complex is degraded by free enzyme. 7. Parallel studies with trypsin indicated that it too forms a 1:1 complex with inhibitor and is degraded by excess of enzyme.


Jan 1, 1977·International Journal of Peptide and Protein Research·M T PlancotG Biserte
Jul 22, 1982·Nature·R W CarrellD R Boswell
May 7, 2002·The Journal of Biological Chemistry·Steven W GriffithsCharles L Cooney
Jul 1, 1982·International Journal of Peptide and Protein Research·C B GlaserJ Martin
Feb 1, 1978·European Journal of Biochemistry·J O JeppssonM Fagerhol
Nov 16, 2006·Vox Sanguinis·T P Zimmerman
Nov 1, 1978·International Journal of Peptide and Protein Research·C B Glaser, L Karic

Related Concepts

Circular Dichroism, Vibrational
Hydrogen-Ion Concentration
Isoelectric Focusing
Protein Conformation
Sulfhydryl Compounds

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