Aquaporins are crucial for life in any form and they are found in all organisms, from bacteria via plants to man. Aquaporins facilitate rapid, highly selective water transport, thus allowing the cell to regulate its volume and internal osmotic pressure according to hydrostatic and/or osmotic pressure differences across the cell membrane. The physiological importance of the aquaporin in human is perhaps most conspicuous in the kidney, where ~150-200 liters of water need to be reabsorbed from the primary urine each day, that is, aquaporin facilitated water transport is invoked when water rapidly must be retrieved from a body fluid. The high reabsorption is reflecting the high transport rate of the individual aquaporin proteins: each functional unit can transport on the order of one billion water molecules per second. In 2003 the Nobel Prize in chemistry was awarded to Professor Peter Agre for his discovery of the aquaporin water channel.
Based on aquaporin protein structural information, detailed computer models have revealed how the high water permeation rate and the strict water selectivity is established. In essence, the architecture of the aquaporin channel allows water molecules to pass only in single file while electrostatic tuning of the channel interior controls aquaporin selectivity against any charged solutes. Some aquaporin protein isoforms can transport other compounds such as glycerol, but for the class of ‘orthodox’ aquaporins only water molecules pass through the aquaporin water pore, nothing else.
The physiological roles of water channels in both eukaryotic and prokaryotic organisms have been elucidated and their roles in living cells are becoming increasingly well documented. The understanding of aquaporins and their role in life has opened the possibility of using aquaporins in an industrial context. The goal of Aquaporin A/S is to use aquaporins as building blocks in water filtering devices to be employed in industrial and household water filtration and purification.