Chloroplasts metabolism

Halliwell, B. (1984). Chloroplast Metabolism. Oxford Clarendon Press. 

Halliwell B. Chloroplast Metabolism. The Structure and Function ofChloroplasts in Green Leaf Cells, Clarendon Press, New York, 1984. 

Another aspect of chloroplast metabolism is synthesis of starch. Formation of ADP-glucose from glucose 1-phosphate is induced by 3-phosphoglycerate, a "feed-ahead" type of regulation (Fig. 23-36). Although fructose 2,6-bisphosphate is absent from chloroplasts, it has an important regulatory function in the cytoplasm of plants as it does in animals.425 430 In the plant cytosol triose phosphates from the chloroplasts are converted to fructose 6-P, glucose 6-P, UDP-... 

MAAs can have an inhibitory effect on macroalgae. MAAs added to culture medium retard the growth of Porphyra yezoensis.19 The response is additive the higher the concentration of MAAs, the greater the inhibition of growth. The decline in growth is attributed in part to MAA interference with chloroplast metabolism. Whether this is a direct inhibitory effect or interference with feedback regulatory mechanisms is not yet known. 

Halliwell, B. Chloroplast Metabolism the Structure and Function of Chloroplasts in Green Leaf Cells Oxford Univ. Press England, 1981. Gregory, R. P. F. Biochemistry of Photosynthesis, 2nd ed. John Wiley Sons London, 1977. 

For the past 15 years it was believed that chloroplast metabolism was adversely affected by relatively mild leaf water deficits. However, in recent years a number of investigators have come to the conclusion that water stress does not affect the biochemical reactions of the chloroplast until well after other plant growth processes are affected (1-3). 

B. Halliwell, Chloroplast Metabolism, Clarendon Press, Oxford (1981). 

Chloroplasts—Metabolism. 3. Mitochondria—Metabolism. QH603.M5 T998m] QH601.M466 574.875 75-4744... 

Chloroplasts are the site of photosynthesis, the reactions by which light energy is converted to metabolically useful chemical energy in the form of ATP. These reactions occur on the thylakoid membranes. The formation of carbohydrate from CO9 takes place in the stroma. Oxygen is evolved during photosynthesis. Chloroplasts are the primary source of energy in the light. 

The photosynthetic COg fixation pathway is regulated in response to specific effects induced in chloroplasts by light. What is the nature of these effects, and how do they regulate this metabolic pathway ... 

Understanding mechanisms controlling metabolon localization in plastids of different membrane architectures Little is known about metabolon structure, assembly, and membrane targeting. The carotenoid biosynthetic pathway exists on plastid membranes. However, plastids have different membrane architectures and therefore tissue- and plastid-specific differences in membrane targeting of the biosynthetic metabolon can be expected. Localization in chloroplasts that harbor both thylakoid and envelope membranes differs from the envelope membranes in endosperm amy-loplasts. In fact, localization on both thylakoid and envelope membranes implies that the carotenoid pathway is really not a single pathway, but a duplicated pathway that may very well have membrane-specific roles with regard to functions in primary and secondary metabolism. 

Those striking bluelight-induced morphological responses such as phototropism, induction of polarity of spores or rearrangement of chloroplasts, are necessarily preceded by metabolic bluelight effects. However, no clear-cut causal reaction chain has yet been elucidated. 

Marques, I.A. and L.E. Anderson. 1986. Effects of arsenite, sulfite, and sulfate on photosynthetic carbon metabolism in isolated pea (Pisum sativum L., cv Little Marvel) chloroplasts. Plant Physiol. 82 488-493. 

Polyphenol oxidase occurs within certain mammalian tissues as well as both lower (46,47) and higher (48-55) plants. In mammalian systems, the enzyme as tyrosinase (56) plays a significant role in melanin synthesis. The PPO complex of higher plants consists of a cresolase, a cate-cholase and a laccase. These copper metalloproteins catalyze the one and two electron oxidations of phenols to quinones at the expense of 02. Polyphenol oxidase also occurs in certain fungi where it is involved in the metabolism of certain tree-synthesized phenolic compounds that have been implicated in disease resistance, wound healing, and anti-nutrative modification of plant proteins to discourage herbivory (53,55). This protocol presents the Triton X-114-mediated solubilization of Vida faba chloroplast polyphenol oxidase as performed by Hutcheson and Buchanan (57). 

Chloroplasts are a typical type of plastid that performs various metabolic reactions as well as photosynthesis. Their envelope consists of two membranes the outer envelope membrane and the inner membrane (Fig. 7). The space between these two membranes is called the intermembrane space, and the space enclosed by the inner envelope membrane is called the stroma. In addition, chloroplasts have another membrane system within the stroma the thylakoid membrane forms the lumen. Therefore, there are six different localization sites and, of course, multiple pathways to each site. Naturally, their sorting mechanisms are very complicated. 

Nobel and Wang reported that the permeability of the outer membranes of chloroplasts was increased by exposure to ozone (at 30 ppm for 5 min). They hypothesized that the effect was lipid oxidation. Freebaim showed that ozone inhibited respiratory activities of isolated mitochondria, and Lee found that the effect of ozone on oxidative phosphorylation was greater than on oxygen uptake. Mudd et reported that the metabolism of UDP-galactose by isolated... 

It is generally accepted that chloroplasts possess an intact pathway of aromatic amino acid biosynthesis that is tightly regulated. In addition, the subcellular location of some aromatic-pathway isozymes has been shown to be in the cytosol, but whether an intact pathway exists in the cytosol has not yet been proven. The evidence bearing on aromatic amino acid compartmentation and regulation is reviewed, with particular emphasis given to the relationship between primary biosynthesis and secondary metabolism in the cytosol. 

The tightly regulated pathway specifying aromatic amino acid biosynthesis within the plastid compartment implies maintenance of an amino acid pool to mediate regulation. Thus, we have concluded that loss to the cytoplasm of aromatic amino acids synthesized in the chloroplast compartment is unlikely (13). Yet a source of aromatic amino acids is needed in the cytosol to support protein synthesis. Furthermore, since the enzyme systems of the general phenylpropanoid pathway and its specialized branches of secondary metabolism are located in the cytosol (17), aromatic amino acids (especially L-phenylalanine) are also required in the cytosol as initial substrates for secondary metabolism. The simplest possibility would be that a second, complete pathway of aromatic amino acid biosynthesis exists in the cytosol. Ample precedent has been established for duplicate, major biochemical pathways (glycolysis and oxidative pentose phosphate cycle) of higher plants that are separated from one another in the plastid and cytosolic compartments (18). Evidence to support the hypothesis for a cytosolic pathway (1,13) and the various approaches underway to prove or disprove the dual-pathway hypothesis are summarized in this paper. 

Aromatic amino acids interface with a diverse and vast network of connecting secondary metabolism in the cytosol, but not in other major compartments such as the chloroplast. A strong rationale and emerging lines of experimental evidence support the probable existence of an intact cytosolic pathway of aromatic amino acid biosynthesis which links carbohydrate metabolism (via PEP and erythrose-4-P, or possibly glyceraldehyde-3-P) and secondary metabolism. 

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