| Budget Amount *help |
¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1986: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1985: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
The actin-degrading enzyme was extracted from the metamorphosing bullfrog tadpole tail. This enzyme was partially purified and characterized. The molecular weight was determined as 26,000 by the gel chromatography. The enzyme was active in degrading actin molecules in the broad range of pH (5.5 to 7.5) with the maximum activity at pH 6.0, and hydrolyzed native actin, myosin H chain, troponin C and I. To get information on the physiological role of this enzyme, the following investigation was carried out. The tail muscle fibers of prometamorphic tadpole were incubated in vitro with the enzyme after they were treated with saponin to obtain uniform penetration of the enzyme, and ultrastructural changes of the myofibrils in course of time were investigated. The initial changes were seen after 5 min in actin filaments within I-band to be irregular arrangement as like waste threads. Most of the I-bands and Z-discs disappeared by 15 min so that the myofibrils fragmentized at the level of the I-bands, or the myofilaments fanned out from the terminals of the intact myofibrils. The A-band then overlapped with the neighboring A-bands, but the H-bands including M-lines remained intact.
These ultrastructural changes have many points of resemblance to those of the myofibrils during spontaneous metamorphosis. Therefore, this enzyme was supposed to play an important role in degeneration of the myofibrils of the anuran tadpole tail during spontaneous metamorphosis.
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