1) Absorption occurs throughout the small intestine. 2) Absorption appears to be saturable, active transport process: thougth to be absorbed as Mn2+; DMT1. 3) Dietary absorption ranges from 1-14%: often 5%, women absorb more than men, absorption decreases when intakes are excessive. 4) Histidine and citrate enhance absorption 5) Fiber, phytate, and oxalate inhibit absorption.
Sources of Manganese
Whole grains, nuts, vegetables, and fruits.
Transport and storage
1) Manganese enters the portal circulation: circulates free (Mn2+) or bound to a alpha-2-macroglobulin; liver clears almost all the newly absorbed Mn. 2) Liver secretion: Free Mn2+; albumin or a alpha-2-macroglobulin bound; transferrin bound (requires oxidation to Mn3+ by ceruloplasmin). 3) Manganese is cleared rapidly from blood and accumulates in the mitochondria: Mediated by a Ca-dependent carrier; Manganese is located in most organs and tissues.
Functions and Mechanisms of Action (biochemical)
1) Enzyme activation and a constituent of metalloenzymes 2) Activation of enzyme-catalyzed reactions.
Functions: activation of enzyme-catalyzed reactions
1) Manganese binds to substrates (ATP) or to the enzyme directly, causes a conformational change that activates the enzyme. 2) Enzymes from several classes require Mn: transferases, hydrolases, oxido-reductases, ligases. 3) Other divalent cations (primarily magnesium or cobalt) can replace the manganese in order to keep the enzymes functioning properly during Mn deficiency.
Functions and Mechanisms of action (metabolic)
1) Normal skeletal growth and development. 2) Essential for glucose utilization. 3) Lipid synthesis and metabolism; cholesterol metabolism. 4) Pancreatic function and development. 5) Prevention of sterility. 6) Important for protein and nucleic acid metabolism. 7) Involved in thyroid hormone synthesis.