TAL activity cannot be demonstrated in many PAL preparations and often the activity
towards tyrosine, where it exists, is lost rapidly during purification.’ In Ustilago, not only
is TAL activity not present in crude or purified PAL preparations but p-coumaric acid is not
formed when tyrosine is administered in vivo. 3 In the purification of wheat PAL the PAL/
TAL ratio varied from 4 to 201g and in Sporobolomyces roseus from I.35 to 5.30 The pH
optimum curves of PAL and TAL