E.i. Dupont De Nemours and Company

Ronald Wayne Bussian

Robert C Menson

Venkatachalam Narayanswamy

John A Ruglass

Walter Brent Aitken

The invention is drawn to a diagnostic assay for lactate dehydrogenase isoenzyme LD1 in a sample containing lactate dehydrogenase isoenzymes LD1-LD5. The disclosed assay involves the following steps:

Method for determining lactate dehydrogenase isoenzyme LD1 by

Phosphoenol pyruvate carboxylase is stabilized to have a shelf life of six months or more by incorporating the phosphoenal pyruvate carboxylase in an aqueous solution containing from 0.002 to 0.05 molar sodium phosphate, from 1 to 10, and preferably 3 to 8, m molar aspartate, from 0.02 to 0.1 m molar ethylene diamine tetraacetic acid, from 0.6 to 3.15, and preferably 0.8 to 1.2, molar ammonium sulfate and up to 20 volume percent glycerol. The sodium phosphate acts as a buffer to maintain the pH of the solution at from 6.0 to 6.8.

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Newark, DE, United States of America

Ronald Wayne Bussian