큰입우럭(Micropterus salmoides) 조직의 젖산탈수소효소 및 Monocarboxylate 수송체(MCT) 1, 2, 4

Abstract

The properties of lactate dehydrogenase (EC 1.1.1.27, LDH) and expression of monocarboxylate transporters (MCTs) 1, 2, and 4 were studied in tissues from Micropterus salmoides. Native-PAGE revealed that the LDH isozyme was predominantly located in skeletal muscle. The LDH , , and isozymes were detected in heart, liver, eye, and brain tissues, while eye-specific isozyme was detected in eye tissue. In September, strong LDH isozyme activity was detected in heart tissue. High isozyme activity was noted in all other tissues except heart tissue. However, in November, strong isozyme activity was detected in heart tissue. The LDH/CS (Citrate synthase, EC 4.1.3.7) ratio in skeletal muscle and heart tissues indicated that anaerobic metabolism was high in those tissues. Native-PAGE after immunoprecipitation showed that eye-specific isozyme was more similar to the than the isozyme. The LDH isozyme was purified by affinity chromatography. The molecular weight of subunit A was 37,200. The LDH activity in tissues was consistently 11.05~28.32% due to inhibition by 10 mM pyruvate. The of LDH in eye tissue was very low. The optimum pH for LDH in tissues was pH 7.5~8.0. The LDH isozyme was detected in mitochondria of skeletal muscle, whereas the and isozymes were detected in heart tissue mitochondria. Western blot analysis indicated that MCTs 1, 2, and 4 were located in the plasma membrane and mitochondria of skeletal muscle and heart tissues. The sizes of MCTs 1, 2, and 4 in skeletal muscle were 60, 54~38, and 63 kDa, while those in heart tissue were 57, 54~38, and 55.5 kDa, respectively. In conclusion, M. salmoides appears to use anaerobic metabolism predominantly when adapted to a hypoxic environment. In highly activated skeletal muscle and heart tissue, energy production is controlled by inward and outward flows of pyruvate and lactate through MCTs 1, 2, and 4 in the plasma membrane and mitochondria, with effective adjustment by LDH isozymes.