Which LD isoenzymes are labile in the cold?

Which LD isoenzymes are labile in the cold?

• A. LD-1 and LD-2
• B. LD-3 and LD-4
• C. LD-4 and LD-5
• D. LD-2 and LD-3

Answer: (C)

When studying LD isoenzymes, the stability of each form can vary with temperature. In cold storage, some isoforms lose activity faster than others. The LD-4 and LD-5 forms, which feature more M-subunit composition, are particularly prone to inactivation in the cold, so their activities drop if a specimen is refrigerated. This makes them the labile ones in the cold. In contrast, the other LD forms are comparatively more stable when chilled, so refrigeration has less impact on their measured activities. For accurate LD isoenzyme analysis, specimens are best handled at room temperature or processed promptly to preserve LD-4 and LD-5 activities.

When studying LD isoenzymes, the stability of each form can vary with temperature. In cold storage, some isoforms lose activity faster than others. The LD-4 and LD-5 forms, which feature more M-subunit composition, are particularly prone to inactivation in the cold, so their activities drop if a specimen is refrigerated. This makes them the labile ones in the cold. In contrast, the other LD forms are comparatively more stable when chilled, so refrigeration has less impact on their measured activities. For accurate LD isoenzyme analysis, specimens are best handled at room temperature or processed promptly to preserve LD-4 and LD-5 activities.