Catalyzes the conversion of p-hydroxyphenylacetaldoxime to p-hydroxymandelonitrile. The dehydration of the oxime to the corresponding nitrile is followed by a C-hydroxylation of the nitrile to produce p-hydroxymandelonitrile. (E)-4-hydroxyphenylacetaldehyde oxime + O2 + reduced [NADPH--hemoprotein reductase] = (S)-4-hydroxymandelonitrile + H(+) + 2 H2O + oxidized [NADPH--hemoprotein reductase] Secondary metabolite biosynthesis; dhurrin biosynthesis; dhurrin from L-tyrosine: step 2/3. Belongs to the cytochrome P450 family.