Fast enzymatic preparation of L-dopa from tyrosine and molecular oxygen: a potential method for preparing [15O]L-dopa

A fast, simple and inexpensive enzymatic preparation of 3,4-dihydroxyphenyl-L-alanine (L-DOPA) from molecular oxygen and tyrosine using mushroom tyrosinase is described. The theoretical incubation time for production of [15O]L-DOPA with maximal specific activity from [15O]O2 can be calculated to be about 3 min. In practice, using a specially-designed glass reaction chamber to facilitate the incorporation of gaseous molecular oxygen into L-DOPA with zero lag-time, a 3 min reaction with 1% oxygen in nitrogen results in the formation of approx. 3.9 mumols of L-DOPA, representing conversion of about 14% of the tyrosine substrate. Given access to a supply of [15O]O2, the method should be applicable to the preparation of [15O]L-DOPA for use as a PET tracer.