Phosphorylases localization

C. It is secreted along with noradrenaline by the adrenal medulla, from which it may be obtained. It may be synthesized from catechol. It is used as the acid tartrate in the treatment of allergic reactions and circulatory collapse. It is included in some local anaesthetic injections in order to constrict blood vessels locally and slow the disappearance of anaesthetic from the site of injection. Ultimately it induces cellular activation of phosphorylase which promotes catabolism of glycogen to glucose. 

Idoxuridine (9.7) and trifluridine (9.8) are antiviral agents that are phosphorylated to their active form in virus-infected cells, and thus show specificity for two reasons their higher affinity for the viral enzyme, and the higher phosphorylase levels in viral-infected than in normal cells. Both compounds have been used locally on lesions of HSV-1 and HSV-2 (the latter of which causes genital herpes, now reaching epidemic proportions) with fair success. They are rather toxic if administered parenterally, as are all moderately selective antimetabolities. 

Willnecker, Jahnke and Buehner96 reported recently the preliminary results of X-ray crystallographic analysis of the potato type-L isozyme at 2.6 A resolution, and showed that the overall folding of the potato phosphorylase is essentially the same as that of the rabbit muscle enzyme (more similar to the 7 -form than to the T-form). Only small differences were found in the core of the subunit, although local structures on the surface including the loops deviated significantly, being consistent with the sequence differences with some minor insertions and deletions as compared with the rabbit muscle enzyme (see above). As... 

A. The DADMe modification also provides a favorable charge localization to place the cation at the l -position. The pKa of l -pyrrolidine nitrogen in DADMe system is 8.575 and provides the cationic nitrogen to ion pair with phosphate in the active site of phosphorylases. The N4 nitrogen of Immucillin-H has a pKa of 6.972 and is cationic in the active site, however the Cl -C9 distance is only... 

Each monomer contains one pyridoxal phosphate and a highly conserved primary structure in the vicinity of the cofactor binding site. The enzymes follow the same catalytic mechanism, a rapid equilibrium random Bi Bi mechanism. However, unlike animal phosphorylases, the microbial and plant enzymes are not subjected to covalent or allosteric control. Within the group of higher plant phosphorylases two types of enzyme have been distinguished which differ in monomer size, peptide pattern, glucan specificity, and intracellular location (1-3). Based on immunochemical studies on leaf tissues (4-5), one enzyme form has been localized in the cytosol whereas the other one resides in the chloroplast. Thus, the two plant phosphorylase types represent non-interconvertible proteins which presumably have entirely different metabolic functions. 

Cotyledons of developing or germinating pea seeds contain two forms of glucan phosphorylase which are electrophoretically and immunologi-cally identical with the cytosolic (isozyme I) and the plastidic (enzyme III cf. 6) phosphorylase form from pea leaflets. For pea cotyledons the dual intracellular location of phosphorylase was ensured by indirect immunofluorescence. Using this technique, isozyme I was localized in the cytosol of parenchyma cells of cotyledons whereas the other isozyme was visualized in the stromal space of amyloplasts or proplastid-like organelles (data not shown). 

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