Oleate hydroxylase involved in the biosynthesis of ricinoleate (PubMed:7624314, PubMed:27056057). It uses cytochrome b5 as an electron donor (PubMed:1417766). May act on both oleic acid (18:1(9cis)) and eicosenoic acid (20:1(11cis)) (PubMed:8784737). 1-acyl-2-(9Z)-octadecenoyl-sn-glycero-3-phosphocholine + 2 Fe(II)-[cytochrome b5] + 2 H(+) + O2 = 1-acyl-2-[(R)-12-hydroxyoleoyl]-sn-glycero-3-phosphocholine + 2 Fe(III)-[cytochrome b5] + H2O (9Z)-octadecenoate + AH2 + O2 = (12R)-hydroxy-(9Z)-octadecenoate + A + H2O Inhibited by oleoyloxyethyl phosphocholine. Optimum pH is 6.3. Optimum temperature is 22.5 degrees Celsius. Lipid metabolism; monounsaturated fatty acid biosynthesis. Expressed in seeds. Barely detected in leaves. Accumulates progressively during seeds development. The histidine box domains may contain the active site and/or be involved in metal ion binding. Promotes the accumulation of hydroxy fatty acids when expressed in A.thaliana. Belongs to the fatty acid desaturase type 1 family.