MDH（EC 1.1.1.37）is widely exist in animal, plant, microbe and cells culture. MDH in mitochondria is
one of the key enzymes of TCA cycle, which catalyzes the formation of oxaloacetic acid from malic acid.
In contrast, MDH in serum catalyzes the formation of malic acid from oxaloacetic acid. Oxaloacetic acid is
an important intermediate that connects several important metabolic pathways. MDH plays an important
role in many physiological activities of cells, including mitochondrial energy metabolism, malic acid-
aspartic acid shuttle system, reactive oxygen species metabolism and disease resistance. According to the
different coenzyme specificity, MDH is divided into NAD- dependent MDH and NADP- dependent MDH.
NADP-MDH is mainly present in eukaryotic cells.
NADP-MDH catalyzes NADPH to reduce oxaloacetic acid into malic acid, resulting in a decrease in
absorption at 340 nm.
Required but Not Provided:
Ultraviolet spectrophotometer/microplate reader, desk centrifuge, water-bath, adjustablepipette, micro
quartz cuvette/96-well flat-bottomUV plate and distilled water.
Protocol
I. Preparation:
1. Cells or bacterial
Collect bacteria or cells into the centrifuge tube. Discard the supernatant after centrifugation. It is
suggested to take about 2 million bacteria/cell and add 400 μL ofExtractsolution. Bacteria/cell is split by
ultrasonic (power 20%, ultrasonic 3s, interval 10s, repeat for 30 times). Centrifuge at 8000 g 4℃ for 10
minutes. Take the supernatant on ice for test.
2. Tissue:
