Arginine catabolism in the cotyledons of developing and germinating pea seeds

Arginine is the predominant free amino acid in the cotyledons of developing seeds of Pisum sativum L. cv Marzia. Breakdown of arginine was measured by injecting l-[guanido-¹⁴C]arginine into detached cotyledons. Cotyledons of developing seeds showed a low rate of ¹⁴CO₂ evolution whereas a much higher rate of ¹⁴CO₂ evolution was measured from cotyledons of seeds 4 days after the onset of germination. The activities of the catabolic enzymes arginase, urease, and ornithine aminotransferase were measured throughout development and germination. Arginase and ornithine aminotransferase were present at an early stage of development. Urease activity appeared later as the seeds started to desiccate. During germination, all three enzymes were present. The different course of activity of these enzymes indicates that they are controlled separately.     

Characteristics of NADPH-dependent thymidylate synthetase purified from Streptomyces aureofaciens.

NADPH-dependent thymidylate synthetase from Streptomyces aureofaciens has been purified to homogenity by a two-step chromatographic procedure including anion-exchange chromatography and affinity chromatography on methotrexate-Sepharose 4B. The enzyme was purified 1025-fold with a 34% yield. Basic characteristics of the enzyme were determined: molecular weight of the enzyme subunit (28,000), pH and temperature optimum, effect of cations, dependency on reducing agents, Km values for dUMP, mTHF, and NADPH (3.78, 21.1, and 38.9 microM, respectively), and inhibition effect of 5-FdUMP. Binding studies revealed the enzyme mechanism to be ordered sequential: dUMP bound before mTHF. S. aureofaciens thymidylate synthetase exhibits an absolute requirement for NADPH for the enzyme activity--a unique feature not displayed by any of the thymidylate synthetases isolated so far. NADPH is not consumed during enzyme reaction, indicating its regulatory role. The properties of S. aureofaciens thymidylate synthetase show that it is a monofunctional bacterial enzyme.     

Changes in glycosidase activities during galactoglucomannan oligosaccharide inhibition of auxin induced growth

The inhibition of 2,4-D-induced elongation growth by galactoglucomannan oligosaccharides (GGMOs) in pea stem segments (Pisum sativum L. cv. Tyrkys) after 18 h of incubation results in changes of extracellular, intracellular and cell wall glycosidase activities (beta-D-glucosidase, beta-D-mannosidase, beta-D-galactosidase, beta-D-xylosidase, alpha-D-galactosidase, and alpha-L-arabinosidase). GGMOs lowered the glycosidase activities in the extracellular fraction, while in the cell wall fractions their activities were markedly increased. The intracellular enzyme alpha-d-galactosidase increased while the beta-d-galactosidase decreased in activity in response to the GGMO treatment. Extracellular enzymes showed low values of activities in comparison with intracellular and cell wall glycosidases. It is evident that GGMOs can alter auxin induced elongation and glycosidase activities in different compartments of the cell, however, the mode and site of their action remains unclear.     

Anisotropy decay study on the host-guest interaction of distally dialkylated calix[4]arenes with 1-chloro-4-(trifluoromethyl)benzene

The 'host' properties of distally dialkylated calix[4]arenes and 4-tert-butylcalix[4]arenes in the presence of 1-chloro-4-(trifluoromethyl)benzene (BFT) were studied in chloroform solvent by intensity-independent spectrofluorometric method. The anisotropy decay experiments were found as suitable method to indicate the host-guest complex formation but it is unable to determine the strength of supramolecular interaction.     

Three generations of alpha,gamma-diaminobutyric acid modified poly(propyleneimine) dendrimers and their cisplatin-type platinum complexes

Three generations of alpha,gamma-diaminobutyric acid modified poly(propyleneimine) dendrimers [DAB(AM)n, n = 4, 8, 16] containing 4, 8, 16 free amino groups were coupled with Boc-protected alpha,gamma-diaminobutyric acid (DABA) moieties in high yields. These modified dendrimers were deprotected and the chiral dendritic amines with 8, 16 and 32 amino groups on the surface were isolated in excellent yields. Dendrimers with cisplatin moieties at the periphery were obtained in the reaction of the free amine dendrimers and potassium tetrachloroplatinate(II). The highly insoluble complexes were isolated as hydrates and characterized by means of IR, TGA and elemental analysis.