Ricinoleate biosynthesis in castor microsomes

• Published in: Industrial crops and products 1997, Vol.6 (3), p.383-389
• Main Authors: McKeon, T.A, Lin, J.T, Goodrich-Tanrikulu, M, Stafford, A.E
• Format: Article
• Language: English
• Subjects: biosynthesis; coenzyme A; enzyme activity; enzyme inhibitors; glycolipids; microsomes; Oilseed; oleoyl desaturase; Oleoyl hydroxylase; oleoyl-12-hydroxylase; oxygenases; Plant lipids; ricinoleic acid; Ricinus; Ricinus communis
• ISSN: 0926-6690; 1872-633X
• DOI: 10.1016/S0926-6690(97)00029-0

Oleoyl-12-hydroxylase is the enzyme responsible for ricinoleate biosynthesis in castor ( Ricinus communis). The hydroxylase introduces the mid-chain hydroxyl group, resulting in a fatty acid with numerous chemical uses. To determine conditions for high levels of ricinoleate production, it is important to characterize the hydroxylase activity in isolation from interfering activities. However, progress in purifying this enzyme has been limited by the inability to solubilize and reconstitute the enzyme activity from microsomes. By using low levels of microsomal protein (12–35 μg) and following conversion of 14C-oleoyl-CoA to 14C-ricinoleate, the reaction is linear as a function of time and the rate is directly proportional to amount of protein. Moreover, at the lower levels of microsomal protein, microsomes treated under conditions that solubilize the hydroxylase recover full activity. This represents an important step in developing the ability to reconstitute the hydroxylase activity. Other factors involved in the high level of ricinoleate production by castor are the steady increase in hydroxylase activity throughout development and the decline in oleoyl desaturase. The glycol lipid oleoyloxyethyl phosphocholine is an effective inhibitor of hydroxylase activity, and should prove to be a useful tool in following the movement of labelled fatty acids through lipid pools.