In electrophoresis isoenzyme numbering, which isoenzyme is the fastest migrating?

• A. Isoenzyme 1
• B. Isoenzyme 2
• C. Isoenzyme 3
• D. Isoenzyme 4

Answer: (A)

In electrophoresis, how fast an isoenzyme moves depends on its net charge and size: more negative charge and smaller size generally mean greater mobility toward the opposite electrode, so the fastest form travels the farthest. In isoenzyme numbering, the series is arranged by this migration speed, with the fastest-moving form given the smallest number. So the isoenzyme labeled first in the sequence is the one that migrates the quickest, while the others migrate more slowly as the numbers increase.