Non-cyclic phosphorylation

The participation of the phycobiliproteins in the absorption ofphotokinetically active light has been demonstrated above. Peaks of around 565 and 615 nm in the action spectra indicate the involvement of C-phycoerythrin andC-phycocanin. These pigments transfer energy to the reaction center of PS II and suggest the participation of the non-cyclic electron transport and coupled phosphorylation. 

Biosynthesis of ATP. ATP is the irrunediate product of all cellular processes leading to the chemical storage of energy. It is biosynthesized by phosphorylation of ADP in the course of Substrate phosphorylation (see). Oxidative phosphorylation (see) and non-cyclic Photophosphorylation (see) in plants. Energy in the form of a third phosphate may also be transferred to ADP from other high-energy phosphates, such as creatine phosphate (see Creatine) or other nucleoside triphosphates, or in the adenylate kinase reaction. 

Applying the criteria of Gimmler (1977) for the characterization of the three types of photophosphorylation it is rather difficult to determine the type of the phosphorylation observed. The cyclic phosphorylation can be excluded on account of the fully reduced state of the algae as a consequence of the long anaerobiosis, the applied high light intensity and its insensitivity towards complete inhibition of an electron transport from PS II by DCMU. DCMU prevents photosynthetic O2 evolution and the non-cyclic electron transport. As the observed ATP increase is not affected by DCMU both non-cyclic and pseudocyclic phosphorylation should be ruled out. 

The Horner-Wittig reaction of a-phosphoryl sulphoxides 442, which are chemically stable, results in the formation of a, -unsaturated sulphoxides 443 in high yields (equation 264). The reaction has been found to be non-stereoselective, mixtures of E and Z isomers being formed from aldehydes and unsymmetrical ketones . In the case of aromatic aldehydes this reaction can also be advantageously performed in a two-phase catalytic system even without the usual PTC catalysts (Table 24). Intramolecular Horner-Wittig reaction of a-phosphoryl-5-oxosulphoxides 444 leads to a, -unsaturated cyclic sulphoxides 445 (equation 265). Starting from optically active 0,0-... 

CaMK kinases are Ca2+/calmodulin regulated kinases, while CMGC Pks collect cyclic-dependent, mitogene-activated peptide (MAP) kinases, GSK3 and Clk kinases, that phosphorylate substrates in proline-rich domains. The last group are PTKs (protein tyrosine kinases), which include both receptor and non-receptor kinases, which phosphorylates tyrosine residues (this will be discussed in Sect. 4.3). 

Many other kinases have been studied, often in the context of regulation of some process by phosphorylation and dephosphorylation. Examples from muscle regulation have already been given. A further example is the transcription of eukaryotic DNA, which may be regulated by phosphorylation of non-histone chromosomal proteins. A number of nuclear protein kinases have been partially purified. These have an absolute requirement for divalent cations, and are not stimulated by 3, 5 -cyclic AMP (cAMP).287,288... 

A non-specific bacterial acid phosphatase from Shigella flexneri (PhoN-Sf) has been screened for regioselective phosphorylation of primary alcohol(s) of more than 20 different cyclic and acyclic monosaccharides using pyrophosphate as the phosphate donor (O Scheme 61) [368]. These studies have shown that PhoN-Sf is capable of phosphorylating a range of hexoses (D-glucose epimers, glycosides, and C-2 derivatives), pentoses, heptoses, ketoses, and acyclic carbohydrates. 

Also procedures for the isolation of inside-out membranes, by French Press treatment of intact bacteria, have been described. In phototrophic organisms, these membranes are derived from the invaginations of the plasma membrane and are called chromatophores. These preparations have been extensively used for studies on light-dependent cyclic electron transfer and photophosphorylation. In non-phototrophic bacteria the resulting structures are often called inverted membranes or membrane particles, in analogy with sub-mitochondrial particles. Amongst others, these preparations have been isolated from Azotobacter vinelandii and E. coli. These inverted membranes can be used for the study of oxidative phosphorylation and the determination of H /e stoicheiometries since the enzymatic machinery for these processes is located on the external surface of these membranes. Also excretion of ions (like ) from intact cells can be studied conveniently in these preparations because these ions are accumulated in inverted membranes. 

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