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. 1968 Jun;43(6):979–989. doi: 10.1104/pp.43.6.979

Inositol Metabolism in Plants. V. Conversion of Myo-inositol to Uronic Acid and Pentose Units of Acidic Polysaccharides in Root-tips of Zea mays 1

R M Roberts 1, J Deshusses 1,2, F Loewus 1
PMCID: PMC1086957  PMID: 16656871

Abstract

The metabolism of myo-inositol-2-14C, d-glucuronate-1-14C, d-glucuronate-6-14C, and l-methionine-methyl-14C to cell wall polysaccharides was investigated in excised root-tips of 3 day old Zea mays seedlings. From myo-inositol, about one-half of incorporated label was recovered in ethanol insoluble residues. Of this label, about 90% was solubilized by treatment, first with a preparation of pectinase-EDTA, then with dilute hydrochloric acid. The only labeled constituents in these hydrolyzates were d-galacturonic acid, d-glucuronic acid, 4-O-methyl-d-glucuronic acid, d-xylose, and l-arabinose, or larger oligosaccharide fragments containing these units. Medium external to excised root-tips grown under sterile conditions in myo-inositol-2-14C contained labeled polysaccharide.

When label was supplied in the form of d-glucuronate, the pattern of labeled uronic acid and pentose units in cell wall polysaccharides resembled that obtained from labeled myo-inositol, indicating that both substances were metabolized along a common path during polysaccharide formation, and that methylation occurred at a step subsequent to uronic acid formation. When label was supplied in the form of l-methionine-methyl-14C, 4-O-methyl-d-glucuronic acid was the only labeled monosaccharide component that survived enzymatic or acid hydrolysis.

Zea mays endosperm, a known source of phytin, developed maximal phytase activity after the third day of germination. Results obtained here suggest that myo-inositol released by hydrolysis of phytin represents the initial precursor of a normal, possibly predominant pathway for the formation of uronic acids in plants.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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