Studies on some kinetic parameters of aldolases in selected tissues of the freshwater fish (Tilapia mossambica) under the toxic impact of methyl parathion
✍ Scribed by Prasada Rao S. Kodavanti; K. V. Ramana Rao
- Publisher
- John Wiley and Sons
- Year
- 1989
- Tongue
- English
- Weight
- 572 KB
- Volume
- 9
- Category
- Article
- ISSN
- 0260-437X
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✦ Synopsis
Kinetic parameters of aldolases in muscle, gill, liver and brain tissues of the teleost Tikpia mossambica were studied at sublethal concentrations with methyl parathion (MP). The pH activity profiles were optimal at pH 7.0 and 9.0 in gill, liver and brain tissues, whereas only a single peak at pH 7.0 was observed in muscle tissue of both control and MP-exposed fish. The pH 7.0-specific peak was confirmed as aldolase A and the pH 9.0specific peak represents the tissue-specific aldolases: aldolase B in liver, aldolase C in brain and aldolase B-C in gill. It is further confirmed with the inhibitor sensitivity of aldolases at two peaks with 6 X M ATP or AMP. The pH-based substrate-dependent kinetics of aldolases showed a variable trend. The tissue-specific activity of pH 7.0-specific aldolases showed low K,, values for gill followed by muscle, liver and brain tissues, suggestive of its high enzymesubstrate affinity. During MP exposure, the V, , , values of pH 7.0-specific aldolases in muscle, gill and brain were unchanged compared to controls, but K , values were decreased. The pH 9.0-specific aldolases of gill and liver from MP-exposed fish showed decreased K,,, values with a slight increase in V,,, values. Effectors such as lysine, arginine and CaZ' inhibited, while histidine, cysteine, aspartic acid and a-ketoglutaric acid elevated the activity levels of aldolases. It was concluded that the considerable enhancement in the catalytic efficiency of both the pH 7.0-and ph 9.0-specific aldolases during MP toxicity could be due to a change in the configuration of aldolases or due to a change in the intracellular environment.
L C ~, ,
of MP to T. mossambica was found to be 0.266 ppm for a 48-h exposure period. For the biochemical studies.