A complete understanding of the regulation of ABA biosynthesis ..
Lactosylceramide plays a vital role in the biosynthesis of many glycosphingolipids, and therefore, the biochemical mechanisms involved in its regulation can have a major impact on its bioactivity and that of related compounds. This review focuses on the role of low density lipoprotein (LDL)-mediated regulation of lactosylceramide biosynthesis. We present evidence indictating that in normal cells having functional LDL receptors there is an LDL-mediated suppression of lactosylceramide biosynthesis regulating UDP-Gal: glucosylceramide 1, 4 galactosyltransferase (GalT-2). In contrast, when there is a lack of LDL receptors, as for example in patients with homozygous familial hypercholesterolemia or kidney cancer, LDL enters the cell a LDL receptor-independent pathway (“scavenger pathway”), up-regulates GalT-2 and increases the cellular levels of lactosylceramide. This review also discusses the role of GalT-2, action in signal transduction of oxidized LDL leading to cell proliferation in aortic smooth uscle cells, a hallmark in the pathophysiology in atherosclerosis. A.
Regulation of SL Biosynthesis via a GID-DELLA Signaling Pathway
AB - Ganglioside biosynthesis is strictly regulated by the activities of glycosyltransferases and is necessarily controlled at the levels of gene transcription and posttranslational modification. Cells can switch between expressing simple and complex gangliosides or between different series within these two groups during brain development. The sequential biosynthesis of gangliosides in parallel enzymatic pathways, however, requires fine-tuned subcellular sequestration and orchestration of glycosyltransferases. A popular model predicts that this regulation is achieved by the vectorial organization of ganglioside biosynthesis: sequential biosynthetic steps occur with the traffic of ganglioside intermediates through subsequent subcellular compartments. Here, we review current models for the subcellular distribution of glycosyltransferases and discuss results that suggest a critical role of N-glycosylation for the processing, transport, and complex formation of these enzymes. In this context, we attempt to illustrate the regulation of ganglioside biosynthesis as well as the biological significance of N-glycosylation as a posttranslational regulatory mechanism. We also review the results of analyses of the 5′ regulatory sequences of several glycosyltransferases in ganglioside biosynthesis and provide insights into how their synthesis can be regulated at the level of transcription.
The HMP-PP is produced from aminoimidazole ribotide (AIR) , an intermediate of purine biosynthesis pathway. Hydroxymethyl pyrimidine synthase (ThiC) catalyzes AIR to form hydroxymethl pyrimidine phosphate (HMP-P), which is then phosphorylated to HMP-PP by Hydroxymethyl pyrimidine (phosphate) kinase (ThiD). THZ-P and HMP-PP are coupled to form thiamin monophosphate (ThMP) mediated by thiamin phosphate synthase (ThiE), and thiamin phosphate kinase (ThiL) catalyze a final phosphorylation step to yield ThDP, the active form of thiamin.
Upstream regulation of mycotoxin biosynthesis.
Evans DR and Guy HI (2004) Mammalian pyrimidine biosynthesis: fresh insights into an ancient pathway. Journal of Biological Chemistry 279: 33035–33038.
Biosynthesis, regulation, and domestication of …
Anthocyanins are water-soluble pigments belonging to the flavonoid compound family involved in nature in several aspects of plant development and defense. By bestowing much of the color and flavor on fruits and vegetables, they are components of the human diet and, thanks to their radical-scavenging properties, are not considered exclusively as food products but also as therapeutic agents. Several cultivars of red (or blood) oranges [ (L.) Osbeck], such as Tarocco, Moro, and Sanguinello, are characterized by the presence of anthocyanins in both the rind and fruit juice vesicles. The amount and composition of anthocyanins in the pigmented orange cultivar vary greatly depending on variety, maturity, region of cultivation, and many other environmental conditions. Most of the blood orange varieties require a wide day–night thermal range to maximize color formation. Therefore, the production of red oranges characterized by high anthocyanin levels is limited to a few regions and in particular to the Sicilian area around Mount Etna in Italy, where the characteristic climate conditions yield fruits of unique color intensity and quality. In this review, both the basic information and the most recent advances in red orange anthocyanins are reported, with intense attention given to their biosynthesis and regulation.
Regulation of riboflavin biosynthesis and transport …
The rate of fatty acid synthesis is controlled by the equilibrium between the monomeric and polymeric acetyl-CoA carboxylase. Control of the acetyl-CoA carboxylase enzyme involves phosphorylation-dephosphorylation reactions (3). Metabolically, this conformational change is enhanced by citrate and is inhibited by long-chain fatty acids (i.e. palmitoyl-CoA). The accumulation of citrate in the cytosol of adipose cells shifts equilibrium to the polymeric acetyl-CoA carboxylase, thus activating fatty acid biosynthesis. Palmitoyl-CoA promotes polymer disaggregation and is a primary feedback inhibitor of fatty acid synthesis.
Regulation of ganglioside biosynthesis in the nervous …
Fatty acid biosynthesis occurs through the condensation of C2 units and is coupled to the hydrolysis of ATP (2). The process of fatty acid synthesis involves two regulatory steps. The first step is the carboxylation of acetyl-CoA in the cytosol to form malonyl CoA (Figure 1). Catalyzed by the biotin-dependent acetyl-CoA carboxylase, an enzyme that transfers CO2 to substrates, this step is the rate-limiting step and therefore a very important site in the regulation of fat accumulation. If sufficient biotin is not available for carboxylation of acetyl-CoA, fatty acid synthesis will not occur. The second major point of regulation in fatty acid synthesis is the decarboxylation of the malonyl group, catalyzed by fatty acid synthase. The multienzymatic activity of fatty acid synthase regulates fatty acid synthesis (Figure 2).