Catalyzes the conversion of indole to indolin-2-one. indole + O2 + reduced [NADPH--hemoprotein reductase] = H(+) + H2O + indolin-2-one + oxidized [NADPH--hemoprotein reductase] Secondary metabolite biosynthesis; 2,4-dihydroxy-1,4-benzoxazin-3-one biosynthesis; 2,4-dihydroxy-1,4-benzoxazin-3-one from indoleglycerol phosphate: step 2/5. Belongs to the cytochrome P450 family.