Induction of autoantibodies to human enzymes following viral infection: a biologically relevant hypothesis.

Macro enzymes, i.e. complexes of normal (iso-)enzymes with an immunoglobulin, may be due to immunological cross-reactions evoked by specific viral antigenic determinants that are homologous to regions in the target enzymes. A search of the National Biomedical Research Foundation protein databank with the amino-acid sequence of human pancreatic amylase revealed a marked homology with a fragment of the yellow fever virus major envelope protein E: i.e. an overall identity of 19.7 per cent and a high degree (40.9 per cent) of conservative amino-acid substitutions over 119 amino acids. At each identical position, the corresponding residue of Taka amylase A was examined by three-dimensional structure analysis, to determine whether the position is likely to be buried or exposed. The existence of a site (epitope) on amylase recognized by an anti-amylase antibody is discussed.