Open AccessProperties of Isolated Human α 1 ‐Antitrypsins of Pi Types M, S and Z
Author(s) -
JEPPSSON JanOlof,
LAURELL CarlBertil,
FAGERHOL Magne
Publication year - 1978
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1978.tb12078.x
Subject(s) - sialic acid , pi , isoelectric point , chemistry , thiol , isoelectric focusing , lysine , neuraminidase , biochemistry , thiobarbituric acid , residue (chemistry) , amino acid , stereochemistry , enzyme , lipid peroxidation
1. α 1 ‐Antitrypsin contains a single thiol group partly blocked in native plasma and reactive after mild reduction. 2. Human α 1 ‐antitrypsins of Pi types F, M, S and Z have been isolated with native microheterogeneity using thiol‐disulfide (SH‐SS) interchange reactions utilizing the reactive thiol group. 3. The p I of the various microheterogeneous fractions are given for protein M. Stepwise desialylation of α 1 ‐antitrypsin indicates that the charge difference between the major fractions is one sialic acid residue between each. This is further supported by the p I changes obtained on substitution of the single thiol with positively or negatively charged compounds. 4. Desialylation of purified proteins from each Pi type converts the individual microheterogeneous fractions to one major fraction. The p I shift for the variants studied indicate a difference of plus or minus one or two charge units between protein M and the variants. 5. A difference of one sialic acid residue was obtained for proteins M and Z by the thiobarbituric assay, but stepwise removal of sialic acid with neuraminidase revealed almost identical stepwise change of pattern of both proteins indicating the same number of sialic acid residues. 6. Electrofocusing has been used to identify CNBr fragments from proteins M, S and Z. 7. An amino acid substitution has been found to be located in one of the eight CNBr fragments, glutamic acid in protein M is substituted by lysine in protein Z. 8. The average concentration of α 1 ‐antitrypsin in plasma from healthy males was found to be 1.32g/l.