Phosphorylation, adenosine plant

The second and main biosynthetic pathway of cytokinins in plants is de novo synthesis from phosphorylated adenosine and a precursor of the side chain. Fig. (2). The first and for a long time the only known genes encoding cytokinin de novo synthesizing enzyme, adenylate dimethylallyltransferase (EC 2.5,1.27) also called isopentenyltransferase... 

Ozone has been shown to initiate many physiological and biochemical changes in sensitive plant species. Decreases in photosynthesis and increases and decreases in respiration have occurred in response to ozonation. The bioenergetic status of mitochondria and chloroplasts is disturbed by ozone. Decreases in oxidative- and photo- phosphorylation have been reported as have increases in adenosine triphosphate and total adenylate content of plant tissue. The variable physiological responses appear to be related to the stage of symptom development at the time of analysis and to the mode of ozone exposure, viz. in vivo and in vitro. 

Adenosine kinase is one of a family of nucleoside kinases that are widely found in animal tissues, microorganisms, and plants. This enzyme catalyzes reaction (22), the phosphorylation of the 5 -hydroxyl group of adenosine by MgATP. 

Mitochondria (singular = mitochondrion) are the so-called "power plants" of eukaryotic cells because they are the major source of energy for these cells under aerobic conditions (when oxygen is present). Mitochondria are the sites where complex processes involved in energy generation (such as electron transport and oxidative phosphorylation) are found. The product of mitochondrial action is chemical energy stored in the form of adenosine triphosphate, more commonly called ATP. 

Higher plants and many microorganisms utilise sulphate as their source of sulphur. The initial step in sulphate assimilation involves the action of ATP on sulphate ions to give adenosine-5 -phospho-sulphate (APS). Further phosphorylation by ATP and sulphurylase then occurs and 3 -phospho-adenosine-5 -phosphosulphate (PAPS) is formed. 

Sulfuric acid esters with alcoholic or phenolic hydroxy groups, the mixed anhydrides adenosine-5 -sulfatophosphate and its 3 -phosphorylated derivative, as well as secondary products derived from L-cysteine occur in microorganisms, plants and animals. Sulfuric acid amides, e.g., the glucosinolates (D 9.4), are formed in certain plants. 

Just as in the case of N, the source of the sulphur of higher plants is an oxidized form, namely sulphate. And just like nitrate, sulphate must first be reduced. Ultimately, sulphur is present in the doubly negative form as S. The first step in the assimilation of S is the fixation of sulphate. This is brought about by sulphate reacting with ATP to liberate pyrophosphate. An adenosine-phosphate-sulphate compound is formed and to the ribose of this compound another phosphate residue from another ATP molecule is attached. The product thus obtained is 3 -phosphoryl-5 -adenosine-phosphoryl-sulphate or simply active sulphate (Fig. 114). In this way sulphur is fixed and activated. It is this bound form of active sulphate which is subjected to reduction to the level of S. It is likely that 2 electron transitions are also implicated here. The mechanism is still unknown. 

Mitochondria are the power plants of the living cell their most important roles are to produce the energy of the cell, adenosine triphosphate (ATP) (i.e., phosphorylation of adenosine diphosphate (ADP) by a chain of reactions known as the citric acid cycle or the Krebs cycle) through respiration, and to regulate the cellular metabolism (Fig. 5.1). ... 

D-Ribose 5-phosphate is a normal metabolite in plants and animals. It was first prepared by acid hydrolysis of inosinic acid or from adenosine 5 -phosphate . It is formed enzymically from ribose and ATP . Synthesis has been carried out by phosphorylating 2,3-isopropylidene-methyl-D-ribofuranoside °. ... 

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