Phosphoserine and phosphohydroxypyruvic Acid: evidence for their role as early intermediates in photosynthesis

Photosynthetic fixation of ¹⁴CO₂ in the bean Phaseolus vulgaris, cv. Pencil Pod Black Wax, resulted in the appearance of labeled compounds that were characterized as phosphoserine and phosphohydroxypyruvate by chromatographic separation and by the synthesis of chemical derivatives. In ¹⁴CO₂/¹²CO₂ pulse-chase experiments these metabolites demonstrated the rapid pool saturation and depletion of ¹⁴C characteristic of early intermediates in photosynthetic carbon fixation. They were present in sufficient amounts to account for about 35% of total carbon fixed in 1 minute.