We will look at this pathway in a bit more detail, because it involves themolecule 5-phosphoribosyl--pyrophosphate (which wewill refer to as "PRPP" from now on). PRPP is also involved in thesynthesis of purines and pyrimidines, as we will soon see. In the first step ofhistidine synthesis, PRPP condenses with ATP to form a purine, N1-5'-phosphoribosylATP, in a reaction that is driven by the subsequent hydrolysis of thepyrophosphate that condenses out. Glutamine again plays a role as an amino groupdonor, this time resulting in the formation of 5-aminoamidazole-4-carboximideribonucleotide (ACAIR), which is an intermediate in purine biosynthesis.
Bandurski, R. S., Cohen, J. D., Slovin, J., and Reinecke, D. M. (1995). "Auxin biosynthesis and metabolism". Plant Hormones: Physiology, Biochemistry and Molecular Biology. Dordrecht: Kluwer. pp. 39-65.
to manipulate the biosynthesis of different carotenoids, ..
We demonstrated that the alteration of MAP kinase signal transduction has been simultaneously linked to microalgal carotenoid biosynthesis, other than lipid production.
A steroid is an organic compound with four rings arranged in a ..
Carotenoids also act as antioxidants in the human body. They have strong cancer-fighting properties, according to the Physicians Committee for Responsible Medicine. Some carotenoids are converted by the body to vitamin A, which is essential to vision and normal growth and development. Carotenoids also have anti-inflammatory and immune system benefits and are sometimes associated with cardiovascular disease prevention.
A transcriptional analysis of carotenoid, chlorophyll …
Lutein and zeaxanthin are associated primarily with eye health. Studies often do not separate lutein and zeaxanthin because they are the only carotenoids found in the retina. “Lutein and zeaxanthin are accumulated in human retina at the macula lutea, which is responsible for central vision and protects the retina from blue light, which may cause ionization and damage the retina,” explained Premkumar. Scientists seem to know more about lutein, and supplements typically contain much more lutein than zeaxanthin.
Lecture 02 - Natural Products & Biosynthesis, Web - …
McGaw, B. A. (1995). "Cytokinin biosynthesis and metabolism". Plant Hormones: Physiology, Biochemistry and Molecular Biology. Dordrecht: Kluwer. pp.98-117.
PPT - Biosynthesis PowerPoint Presentation - ID:6736954
Biosynthesis and Metabolism
ABA is a naturally occurring compound in plants. It is a sesquiterpenoid (15-carbon) which is partially produced via the mevalonic pathway in chloroplasts and other plastids. Because it is sythesized partially in the chloroplasts, it makes sense that biosynthesis primarily occurs in the leaves. The production of ABA is accentuated by stresses such as water loss and freezing temperatures. It is believed that biosynthesis occurs indirectly through the production of carotenoids. Carotenoids are pigments produced by the chloroplast which have 40 carbons. Breakdown of these carotenoids occurs by the following mechanism: Violaxanthin is a carotenoid which has forty carbons. It is isomerized and then split via an isomerase reaction followed by an oxidation reaction. One molecule of xanthonin is produced from one molecule of violaxanthonin and it is uncertain what happens to the remaining biproduct. The one molecule of xanthonin produced is unstable and spontaneously changed to ABA aldehyde. Further oxidation results in ABA. Activation of the molecule can occur by two methods. In the first method, an ABA-glucose ester can form by attachment of glucose to ABA. In the second method, oxidation of ABA can occur to form phaseic acid and dihyhdrophaseic acid. The transport of ABA can occur in both xylem and phloem tissues. It can also be translocated through paranchyma cells. The movement of abscisic acid in plants does not exhibit polarity like auxins. ABA is capable of moving both up and down the stem (Walton and Li, 1995; Salisbury and Ross).