Amylase

About: Amylase is a research topic. Over the lifetime, 14164 publications have been published within this topic receiving 296069 citations.

Structural Features of Starch Granules II

Abstract: Publisher Summary Starch granules are commonly found in seeds, roots, tubers, stems, and leaves. Grain seeds, such as maize kernels, contain up to 75% starch on a dry starch basis. The stored starch granules can be converted by enzymes (amylases) to glucose, and the glucose is utilized to generate energy during germination or whenever energy is needed. Starch granules are densely packed with semicrystalline structures and have a density of about 1.5 g/cm3. Because of this stable semicrystalline structure, starch granules are not soluble in water at room temperature. In the granular form, starch can be isolated easily by gravity sedimentation, centrifugation, and filtration, and can be subjected to various chemical, physical, and enzymatic modifications with subsequent washing and processing. There are two major starch polymers: amylopectin and amylose, each having different properties. Biosynthesis of starch granules takes place primarily in the amyloplast. Minor components found in starch granules include polymers of sizes and with properties intermediate between those of amylose and amylopectin, starch lipids, monostarch phosphate ester groups, and proteins, particularly granule-bound starch synthase. Some minor components, especially phospholipids, free fatty acids, and phosphate ester groups, although at low concentrations, can drastically affect the properties of starch pastes and gels. An understanding of the internal organization of starch granules is crucial for scientists and engineers to optimize reaction conditions for chemical, physical, and enzymatic modifications.

Carbohydrate Metabolism and Its Diseases

Abstract: This chapter focuses on the biochemical mechanisms underlying diseases associated with carbohydrate metabolism. The major function of ingested carbohydrates is to serve as energy sources. Carbohydrates are also precursors of essential intermediates for use in synthetic processes. The digestion of carbohydrates in animals begins with the initial contact of the carbohydrates in their food with the enzymes of salivary juice. Starch of plant foods and glycogen of meat are split into their constituent monosaccharides by the action of amylase and maltase. This activity ceases as the food matter passes into the stomach, where the enzymatic action is destroyed by hydrochloric acid. Within the stomach, only a small portion of the ingested carbohydrate is hydrolyzed before passing into the small intestine. In the small intestine, digestion of carbohydrates takes place quickly by the carbohydrate-splitting enzymes contained in the pancreatic juice and in the succus entericus. This chapter begins with a discussion on digestion, absorption, and metabolism of absorbed carbohydrates. The chapter also elaborates concepts related to insulin and carbohydrate metabolism. The subject of blood glucose and its regulation is also explained. The chapter concludes with presenting an overview of the disorders of carbohydrate metabolism and disorders of ruminants associated with hypoglycemia.