虚血脳microsome分画におけるリン脂質代謝関連酵素の変化

THE ACTIVITIES of PHOSPHOLIPASE A, PI-specific PHOSPHOLIPASE C, LIPASE, LYSOPHOSPHOLIPASE AND ACYLCOA:LYSOPHOSPHOLIPID ACYLTRANSFERASE IN ISCHEMIC BRAIN MICROSOMAL FRACTION

　抄録　虚血脳のmicrosorne分画にてphospholipase A （PLA），PI-specific phospholipase C （PP-PLC），lipase,lysophospholipase （LPL）およびacylCoA：lysophospholipid acyltransferase （AcylCoA：LPA）活性を経時的に測定し，虚血脳の膜リン指質代謝を酵素学的にdeacylation-reacylationサイクルとして検討報告した。deacylation酵素のうちPLA,lipaseは虚血の極めて早期より活性化された。LPL活性に関しては虚血の進行に関係がなかった。また，reacylation酵素であるAcylCoA：LPAは虚血の進行に伴い活性が低下した。以上の結果よりこれまで虚血早期から脳内遊離脂肪酸が増加し，リン脂質が低下する機構としてdeacylation酵素の活性化，reacylation酵素の失活が予想されてきたが今回はこれを支持する結果を得た。また，それぞれの酵素に及ぼす，pH,Ca^2＋イオン，ATPの影響を検討したが，虚血時にはこれら因子も膜リン脂質代謝に要であると思われた。

It has been well recongnized that acyl groups of phospholipids play an important role for struc-ture and function of biomembrane. The turnover of these acyl groups in normal brain biomembrane is also well known. Some types of enzymic system related to this turnover has been investigated. Phospholipase A, PI-specific phospholipase C, li-pase, lysophospholipase and acylCoA: lysophos-pholipid acyltransferase belong to these enzymic systems.

In this report, the sequential changes of phos-pholipase A, PI-specific phospholipase C, lipase, lysophospholipase and acylCoA : lysophospholipid acyltransferase activities in ischemic rat brain were examined.

The purpose of this study was to examine theenzymic changes of deacylation-reacylation cycle of biomembrane phospholipid in ischemic brain.

Ischemic brain were produced by decapitation and activities of 5 enzymes were assayed in mic-rosomal fraction.

The activities of phospholipase A, PI-specific phospholipase C, lipase showed high value during early stage of ischemia for 15 or 30 min and then decreased gradually. Lysophospholipase activity was not changed for 120 min. On the other hand, acylCoA : lysophospholipid acyltransferase activity showed gradual decrease from the biginning of ischemia.

There are some reports that in early ischemic stage, the concent of free fatty acids increase, while that of phospholipid decrease.

The present results may suggest that the changes of free fatty acid and phospholipid in ischemic brain are related to these enzymic system.