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Updated: May 20, 2026

Mapping Metabolism: Monitoring Lactate Dehydrogenase Activity Directly in Tissue
Published on: June 21, 2018
Presence of bound substrate in lactate dehydrogenase from carp liver
Nupur Banerjee1, Debasish Bhattacharyya
1Structural Biology and Bioinformatics Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S. C. Mallick Road, Jadavpur, Kolkata 700 032, India.
Abstract:
While attempting to purify UDP-galactose 4-epimerase from carp liver extract at pH 8.0, it was observed that the preparation even after dialysis could reduce NAD to NADH, interfering epimerase assay. The NAD reduction activity and the epimerase were co-eluted in a series of chromatographic steps. Mass spectrometric analysis of semi-purified fraction revealed that carp liver lactate dehydrogenase (LDH) contained bound lactate which was converted to pyruvate in the presence of NAD. The enzyme-bound lactate and the association with epimerase stabilized LDH from trypsin digestion and thermal inactivation at 45 degrees C by factors of 2.7 and 4.2 respectively, as compared to substrate-free LDH. LDH and epimerase do not belong to any one pathway, but are the rate-limiting enzymes of two different pathways of carbohydrate metabolism. Typically, strongly associated enzymes work in combination, such as two enzymes of the same metabolic pathway. In that background, co-purification of LDH and epimerase as reloaded in this study was an unusual phenomenon.
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