Enzyme multipled immunoassay technique

Increasingly, plasma proteins that were once measured exclusively by their catalytic activities and expressed in terms of enzyme units are now being measured by immunoassay techniques, and expressed in terms of concentration (e.g., micrograms per liter). When the results from these very different forms of analysis are compared, there is often little correlation. In many cases, this reflects the fact that proteins can exist in multiple structural forms, differing in conformational properties, in terms of proteolytic cleavage, or in terms of specific forms of post-translational modification (e.g., phosphorylation). While these forms may retain some conserved epitopes, and thus have common immunological properties, structural differences often have a profound effect on their activities. For example, it has been found that the blood protein factor VIII, which is one of the key proteins in the blood clotting cascade, loses its catalytic activity in hemophilia while... 

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