JBC, Vol. 251, Issue 15, 4751-4757, Aug, 1976
Comparison of the chemical, physical, and survival properties of normal and Z-variant alpha-1-antitrypsins
R. R. Miller, M. S. Kuhlenschmidt, C. J. Coffee, I. Kuo and R. H. Glew
A procedure has been developed for the purification of Z-type
alpha-1-antitrypsin (alpha-1-AT) which is rapid, gentle, and results in
good yields. From 4 units (750 ml) of fresh human plasma, obtained from two
individuals possessing the Pizz phenotype, 53 mg of pure Z-type alpha-1-AT
was obtained. The preparation was homogeneous by the criteria of
polyacrylamide gel electrophoresis, both in the presence and absence of
sodium dodecyl sulfate, and by analytical ultracentrifugation. When
compared to pure alpha-1-AT from plasma of individuals possessing the
normal PiMM phenotype, the two proteins were indistinguishable with respect
to amino acid composition, sedimentation coefficient (s20w of 3.33 for both
M and Z), molecular weight (51,000 by sodium dodecyl sulfate gel
electrophoresis and 47,000 by sedimentation equilibrium for both M and Z),
and trypsin-combining ratio (0.91 for Z and 0.99 for M). The only
difference which was observed between the variant forms of alpha-1-AT was
in the carbohydrate composition. The Z-type alpha1-AT contains between 20
and 25% less carbohydrate than the M-type alpha-1-AT. Specifically, the
Z-type alpha-1-AT is deficient in 1 glucosamine residue, 3 neutral sugar
residues (1 mannose and 2 galactose), and 2 sialic acid residues. Although
the Z-variant is deficient in sialic acid, its survival time in the serum
of a rabbit was not significantly different from that of M-type alpha-1-AT.
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