I. Studies on the Acid Phosphatases of Green Leaves. II. Studies on the Role of Indoleacetic Acid in Cell Elongation

Citation

Boroughs, Howard James (1953) I. Studies on the Acid Phosphatases of Green Leaves. II. Studies on the Role of Indoleacetic Acid in Cell Elongation. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/H6ZH-WM47. https://resolver.caltech.edu/CaltechETD:etd-04212003-115806

Abstract

The bulk protein of green leaves has been shown to be dissociable and probably distinct from the acid phosphatase previously associated with it. This conclusion is based on the differential sedimentation rates in the analytical ultracentrifuge of the bulk protein and of phosphatase, on the relative amount of enzyme present in the bulk protein prepared by salt-precipitation or by differential centrifugation, and on the comparative stability of the two proteins toward heat and acid. Leaf phosphatase is further shown to be a mixture of isodynamic enzymes with different pH optima and Michaelis constants. A separation was accomplished by adsorption, dialysis, and by antigen-antibody reactions. The phosphatases are shown to lose enzymatic activity during dialysis, but to be capable of reactivation by certain metal ions. Copper ions are the most effective activators. Comparison of the spectrographic analysis of the ash of dialyzed phosphatase with enzymatic activity, however, disclosed a direct relation between activity and the amount of iron and manganese, as well as copper. Various comparative aspects of the enzymes were also studied. The influence of auxin on metabolic pathways is studied by a new method, in which the rate of incorporation of isotopically labeled intermediates into varied components of living tissue is studied as a function of the auxin supplied. It is found that auxin is without effect on the total protein amino nitrogen, or on the rate of incorporation of the C[superscript 14] label from glycine or leucine into tissue proteins of Avena and corn coleoptiles. Hence, auxin has no effect on protein metabolism during cell elongation. Similarly, auxin exerted only small effects on the rate of incorporation of C[superscript 14] from acetate into the lipid constituents of Avena coleoptiles. Added auxin induced no important changes in the incorporation of the C[superscript 14] of acetate or sucrose into the cell wall components of Avena. It was shown, however, that absence of auxin favors incorporation of the isotopic label of acetate or sucrose into the pectates and soluble polyuronide hemicelluloses, while the presence of auxin favors incorporation into the non-cellulosic polysaccharides. These effects are of small magnitude in relation to gross increase in cell length.

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