l-Phenylalanine Ammonia-Lyase Activity During Germination of Phaseolus vulgaris

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Abstract
L-Phenylalanine ammonia-lyase (PAL) activity develops in excised bean axes after approximately 5 hr. of incubation and reaches a maximum level after 14 hr. of incubation. Light does not affect the development of activity, but puromycin, cycloheximide, actinomycin D, and 5-fluorouracil inhibit. During this period of incubation both D- and L-p-fluorophenylalanine stimulate fresh weight increase and both inhibit the development of PAL activity. Neither L- nor D-phenylalanine stimulates fresh weight increase while the former inhibits development of PAL activity and the latter has no effect. Neither D isomer is deaminated while L-p-fluorophenylalanine is deaminated at about 1/2 the rate of L-phenylalanine. It is suggested that fluorophenylalanine does not stimulate the fresh weight increase by its effects on the phenol-ics pathway. Trans-cinnamic acid was found to inhibit both the development of PAL activity and the in vitro deamination of L-phenylalanine. Various hydroxycinnamic acids, although inhibiting the development of PAL activity, had little or no effect on the in vitro deamination of L-phenylalanine. The pattern of PAL development in intact seedlings differs markedly from that which occurs in the excised axes, although light also has no effect on the course of activity.