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Abstract
A woman who had no known underlying diseases showed a persistent elevation (about
300 U/L) of serum aspartate aminotransferase (AST) without other abnormal laboratory
findings. Cellolose gel electrophoresis showed that the AST activity in the patient
had an atypical band with slower mobility than normal AST. When the sera from the
patient and from a patient with acute hepatitis were mixed, the atypical band increased
in density and the band of normal size AST disappeared. When the serum was fractionated
on Sephadex G-200 gel filtration medium, almost all AST activity was found between
the void volume and the γ-globulin fraction. However, the AST activity in this fraction
was not retained on dissociation into small AST by acid treatment. This suggests the
loss of enzyme activity in dissociated small AST. The patient's serum was then incubated
with iodine 125-labeled porcine AST; when this was fractionated on gel filtration
medium, the main radioactivity was eluted in the void volume fraction. The binding
activity for 125I-porcine AST was found in the γ-globulin fraction obtained by gel filtration. The
affinity constant of 125I-porcine AST binding to the γ-globulin fraction was 10 × 10−8 mol/L by Scatchard analysis. The binding γ-globulin appeared to be (polyclonal) IgG,
and the binding site was located in F(ab′)2 and Fab fragments. The IgG could be bound with both human and porcine AST but not
with chick AST. Thus the IgG appears specific for AST of mammalian species. These
experimental results suggest that the prolonged elevation of serum AST in our patient
may result from the presence of an ![Math Eq]()
complex, and with excess AST-binding IgG in circulation.
complex, and with excess AST-binding IgG in circulation.Abbreviations:
AST (aspartate aminotransferase), mAST (macromolecular AST), PEG (polyethylene glycol), sAST (soluble AST), TRIS (tris(hydroxymethyl)aminomethene)To read this article in full you will need to make a payment
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Article info
Publication history
Accepted:
February 16,
1994
Received in revised form:
October 18,
1993
Received:
May 21,
1993
Identification
Copyright
© 1994 Published by Elsevier Inc.
