Inositol Metabolism in Plants. IV. Biosynthesis of Apiose in Lemna and Petroselinum

The biosynthesis of apiose was investigated in cell wall polysaccharide of Lemna gibba G3 (duckweed) and in detached leaves of Petroselinum crispum (parsley). Lemna grown either in short days or in continuous light incorporated ¹⁴C from a medium containing myo-inositol-2-¹⁴C into d-apiosyl and d-xylosyl units of cell wall polysaccharides. Labeled d-apiose was characterized by paper chromatography, by formation of labeled crystalline di-O-isopropylidene d-apiose, and by gas chromatography of trimethylsilyl derivatives of apiose and of its sodium borohydride reduction product, apiitol. Periodate oxidation of labeled apiose revealed 86 to 94% of the ¹⁴C was located in formaldehyde fragments corresponding to C3′ and C4. Comparison of this result with work reported by Grisebach and Doebereiner and by Beck and Kandler supports the conclusion that myo-inositol-2-¹⁴C was converted to d-apiose labeled specifically at C4.     

The Catabolism of Plasma Albumin in the Rabbit : Its rate and regulation

From I¹³¹-albumin studies and previously defined mathematical formulations, rates of breakdown were estimated for native plasma albumin in rabbits. These rates of catabolism per unit weight of animal were remarkably constant and were independent of variations in the steady state values of albumin concentration in the plasma. These results imply that, at least between animals, the breakdown of plasma albumin follows a kinetic process of approximately zero order. It seems plausible that the process operates similarly in individual animals, and hence that albumin is maintained at normal steady state levels in the healthy animal primarily by means of a regulated rate of synthesis.     

Kinetics and mechanism of catalysis by proteolytic enzymes: The kinetics of hydrolysis of derivatives of l-lysine and S-(beta-aminoethyl)-l-cysteine(thialysine)by bovine trypsin

1. Several esters of the α-N-toluene-p-sulphonyl and N-benzoyl derivatives of l-lysine and S-(β-aminoethyl)-l-cysteine have been synthesized. 2. The kinetics of hydrolysis of the esters by bovine trypsin have been compared. Values of k₀ are similar for corresponding derivatives of the isosteric amino acids and deacylation of an acyl-enzyme appears to be rate-determining in each case. There are, however, some quantitative kinetic differences between the various series of substrates.