The complexities of starch biosynthesis in cereal endosperms
L Curtis Hannah1, Martha James
1University of Florida, Program in Plant Molecular and Cellular Biology & Department of Horticultural Sciences, P.O. Box 110690, 2211 Fifield Hall, Gainesville, FL 32611, USA.
Current Opinion in Biotechnology
|April 11, 2008
Summary
Adenosine diphosphate glucose pyrophosphorylase is crucial for controlling starch synthesis in cereal endosperms. Enzyme complexes may explain the specific branching patterns observed in amylopectin, a key starch component.
Area of Science:
- Biochemistry
- Plant Biology
- Molecular Biology
Background:
- Starch is a vital energy source for life and a sustainable alternative to fossil fuels.
- Understanding starch synthesis in cereal endosperms is critical for agriculture and industry.
- Amylopectin, the main starch component, contains complex, non-random branching patterns.
Purpose of the Study:
- To investigate the role of adenosine diphosphate glucose pyrophosphorylase in cereal starch synthesis.
- To explore the reasons behind sequence divergence in the subunits of this key enzyme.
- To review evidence for enzyme complex formation in amylopectin biosynthesis.
Main Methods:
- Analysis of six independent transgenic reports.
- Examination of sequence divergence in enzyme subunits.
- Review of studies on starch biosynthetic enzyme complexes.
Main Results:
- Adenosine diphosphate glucose pyrophosphorylase plays a significant role in regulating starch quantity.
- The study identified an unexpected reason for sequence divergence between the enzyme's subunits.
- Evidence suggests starch biosynthetic enzymes form complexes, potentially directing amylopectin branching.
Conclusions:
- Adenosine diphosphate glucose pyrophosphorylase is a key regulatory enzyme in cereal endosperm starch synthesis.
- Enzyme complex formation is a plausible mechanism for the specific organization of alpha-1,6 branch-points in amylopectin.
- Further research into these complexes could unlock new strategies for starch production and modification.
Related Concept Videos
01:26Biosynthesis of Polysaccharides
Polysaccharides such as glycogen and starch are synthesized from nucleoside diphosphate sugars, primarily uridine diphosphate glucose (UDPG) and adenosine diphosphate glucose (ADPG). These activated glucose donors act as key intermediates in carbohydrate metabolism and biosynthesis. UDPG primarily involves glycogen synthesis in animals and many bacteria, while ADPG plays a fundamental role in starch synthesis in plants and certain bacteria.UDPG is formed when glucose-1-phosphate reacts with...
03:25Chemistry of Carbohydrates
Carbohydrates are an essential part of the diet in humans and animals. Grains, fruits, and vegetables are natural sources of carbohydrates that provide energy to the body, particularly through glucose, a simple sugar that is a component of starch and an ingredient in many staple foods. The stoichiometric formula (CH2O)n, where n is the number of carbons in the molecule represents carbohydrates. In other words, the ratio of carbon to hydrogen to oxygen is 1:2:1 in carbohydrate molecules. This...
01:10Sugars as Energy Storage Molecules
Sugar (a simple carbohydrate) metabolism (chemical reactions) is a classic example of the many cellular processes that use and produce energy. Living things consume sugar as a major energy source because sugar molecules have considerable energy stored within their bonds. Consumed carbohydrates have their origins in photosynthesizing organisms like plants. During photosynthesis, plants use the energy of sunlight to convert carbon dioxide gas into sugar molecules, like glucose. Because this...
01:24Oligosaccharide Assembly
Protein glycosylation starts in the ER lumen and continues in the Golgi apparatus. Glycosyltransferases catalyze the addition of sugar molecules or glycosylation of proteins. Usually, these enzymes add sugars to the hydroxyl groups of selected serine or threonine residues to form O-linked glycans or the amino groups of asparagine residues to form N-linked glycans. Different positions on the same polypeptide chain can contain differently linked glycans.
Multiple sugar molecules that may or may...
Multiple sugar molecules that may or may...
01:34Introduction to Carbohydrates
Carbohydrates, proteins, and fats are the primary macronutrients in the human diet. However, carbohydrates are the most favored source of energy in the body. They can be found in a wide variety of foods, including whole grains, fruit, and vegetables, in various forms, such as sugars, starch, and dietary fiber. Based on their structure, carbohydrates are classified into three main classes— monosaccharides, disaccharides, and polysaccharides. The body's cells can only utilize simple...
01:02Role of Microtubules in Cell Wall Deposition
Microtubules are small hollow tubes in eukaryotic cells. The cell wall microtubules are polymerized dimers of two globular proteins, α-tubulin and β-tubulin, two globular proteins. With a diameter of about 25 nm, microtubules are the widest components of the cytoskeleton. They help the cell resist compression and provide a track along which vesicles move through the cell or pull replicated chromosomes to opposite ends of a dividing cell. Microtubules go through quick cycles of disassembly and...