Concanavalin A binding to brain particulate preparations and its effect on adenylate cyclase.

[³H] -Concanavalin A binding to brain particulate preparations measured by a filtration technique was found to show a characteristic regional specificity with the caudate-putamen area exhibiting the greatest density of concanavalin A (con A) binding sites. The synaptic membranes were shown to be the most highly enriched of the subcellular fractions examined in terms of lectin-binding glycoproteins. Con A was also shown to inhibit the basal adenylate cyclase activity of cerebral, cerebellar, and caudate-putamen particulate preparations in a concentration-dependent manner. This lectin sensitivity of the adenylate cyclase is apparently an intrinsic property of the enzyme complex since a detergent dispersed preparation of the cerebral cortical enzyme was equally inhibited by con A. It is proposed that one of the membrane con A binding sites in brain tissue is a component of the adenylate cyclase system.     

Multiple regulation of nucleoside catabolizing enzymes in Escherichia coli: effects of 3:5'' cyclic AMP and CRP protein.

Summary The regulation of the synthesis of nucleoside metabolizing enzymes has been studied in cya and crp mutant strains of Escherichia coli.The synthesis of the cyt-enzymes, cytidine deaminase and uridine phosphorylase regulated by the cytR gene product, is activated by the cAMP-CRP complex. On the other hand the synthesis of the deoenzymes: deoxyriboaldolase, thymidine phosphorylase, phosphodeoxyribomutase and purine nucleoside phosphorylase, appears to be increased if an active cAMP-CRP complex cannot be formed.It also seems that nucleosides serve as poor carbon sources for cya and crp mutants; this could not solely be explained by low levels of nucleoside metabolizing enzymes nor by a deficiency in nucleoside uptake. Addition of casamino acids stimulated the growth of cya and crp mutants, with nucleosides as carbon sources. When grown on glucose and casamino acids growth could be stimulated by adenine and hypoxanthine nucleosides; these results suggest an impaired nitrogen metabolism in cya and crp mutants.Abbreviations and Symbols cAMP cyclic adenosine 3:5-monophosphate - CRP cAMP receptor protein. Genes coding for: adenyl cyclase - cya cAMP receptor protein - crp cytidine deaminase - cdd uridine phosphorylase - udp thymidine phosphorylase - tpp purine nucleoside phosphorylase - pup; cytR regulatory gene for cdd, udp, dra, tpp, drm, and pup - deoR regulatory gene for dra, tpp, drm, and pup     

Pyrroline-5-carboxylic acid reductase from soybean leaves

Pyrroline-5-carboxylic acid reductase was purified 40-fold from soybean leaves (Glycine max L. var Corsoy). The enzyme was fairly unstable, had a broad pH optimum, and was inactivated by heat and acid; NADH and NADPH both served as cofactors. It had a higher activity with NADH (about 4 ×) compared to NADPH, but a lower K_m for NADPH. NADP⁺ inhibited both the NADH- and NADPH-dependent activity. Sulfhydryl group blocking agents reduced the activity as did the carbonyl blocking agent, NH₂OH. Thiazolidine-4-carboxylic acid and phosphate inhibited the enzyme and proline inhibited only at high concentrations. ATP, GTP, and CTP were all effective inhibitors of both the NADH- and NADPH-dependent activity. Phosphorylated nucleotide inhibition was reversed by Mg²⁺ ions.     

Saccharopine and 2-aminoadipic acid in Reseda odorata

2(S),2′(S)-N⁶-(2′-Glutaryl)lysine (l-saccharopine) and 2(S)-2-aminoadipic acid have been isolated from Reseda odorata. When traditional isolation procedures are used l-pyrosaccharopine (5(S),5′(S)-N-(5′-amino-5′-carboxy-pentyl)-2-pyrrolidone-5-carboxylic acid) is formed from l-saccharopine by lactamisation. The degree of lactamisation during various isolation steps has been studied, The amino acids were identified by IR and PMR spectroscopy and the configurations established by enzymic and polarimetric analyses. The contents of saccharopine and 2-amino-adipic acid have been determined relative to the total nitrogen content at various stages in the growth cycle of R. odorata.