J. Biol. Chem., Vol. 263, Issue 21, 10045-10047, 07, 1988
Lactate dehydrogenase isoenzymes are present in matrix vesicles
R Hosokawa, Y Uchida, S Fujiwara and T Noguchi
Department of Prosthetic Dentistry, Kyushu Dental College, Kitakyushu, Japan.
Matrix vesicles were isolated from epiphyseal growth plates of young
rabbits. Lactate dehydrogenase activity was detected in the isolated matrix
vesicles only in the presence of detergents, suggesting that NADH, the
cofactor for the assay, does not penetrate the membrane of matrix vesicles.
In contrast, the activity of alkaline phosphatase, a marker enzyme of the
outer surface of matrix vesicles, was detected in the matrix vesicles using
p-nitrophenyl phosphate as the substrate both in the presence and absence
of detergents. Lactate dehydrogenase activity was detected only in the
cytosol of chondrocytes of the epiphyseal growth plates but not in other
subcellular fractions, showing that lactate dehydrogenase is not from the
plasma membrane and membranes of intracellular organelles of chondrocytes.
The isolated matrix vesicles contained all five lactate dehydrogenase
isoenzymes but did not possess other cytosolic enzymes. These results show
that lactate dehydrogenase is located in the matrix vesicles and suggest
the presence of a mechanism for the specific uptake of cytosolic lactate
dehydrogenase and the possibility of enzymatic quantification of the matrix
vesicles at various calcification sites.
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