Inositol Metabolism In Plants

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Sporoplasts prepared from mature ungerminated pollen of Lilium longiflorum Thunb. will be used to prepare a suspension of subcellular pollen particles which can be fractionated by gradient density centrifugation to yield "storage bodies", organelles bearing phytin-rich inclusions. These organelles will be studied for their phytase content, notably pH 5 and pH 8 phytases, which have already been isolated and partially purified from whole pollen. Each phytase activity will be purified to homogeniety and studied with regard to substrate requirements, products formed, localization, and possible functions. The question of phytate formation from 1L-myo-inositol-1-P will be examined to determine whether 1L-myo-inositol-1-P synthase or myo- inositol kinase is responsible from the first step of phosphorylation. This will be done by measuring hydrogen isotope exchange at C5 of D-glucose-6-P during its conversion to 1L-myo-inositol-1-P, a procedure used successfully in previous studies of the path of carbon from D-glucose-6-P to UDP-D-glucoronate and cell wall products of glucoronate metabolism. The significance of this research is explaining the role of phosphate in regulating plant metabolism. Phytate is a phosphorus storage compound of crucial importance yet practically nothing is known of how it is made by the plant. Phosphates play important regulatory roles in carbohydrate metabolism which in turn determines plant productivity.***//