In order to ensure that reactions happen on time scales conducive to life, humans and other living organisms employ many different enzymes, or biological catalysts. Enzymes are proteins that make chemical reactions happen faster than they otherwise would. Lipases are enzymes that are responsible for breaking down lipids, or fats. There are many different kinds of lipase in nature.
Pancreatic Lipase
The lipase considered most generic or "characteristic" of lipase enzymes by biochemists is pancreatic lipase, or digestive lipase. These enzymes are secreted into the small intestine by the pancreas, and serve the purpose of breaking dietary fats into smaller pieces so that they can be absorbed by the small intestinal lining. Notes Dr. Lauralee Sherwood in her book, "Human Physiology," dietary fats are too large to cross the lining of the small intestine whole. Instead, for humans to benefit from consumed fat, lipase from the pancreas must break the fat up into three smaller pieces, which cross the membrane without difficulty.
Phospholipase
Cell membranes are made up of many types of lipids, but phospholipids are the most numerous of these. Breaking down phospholipids, as would be necessary in digesting the membranes of ingested cells, for instance, requires an enzyme specific to phospholipid digestion--namely phospholipase. Because phospholipase can break down the lipid components of cell membranes, it has the ability to essentially "liquify" cells, explain Drs. Mary Campbell and Shawn Farrell in their book, "Biochemistry." As such, some animals use phospholipids as components of venom to predigest their prey. Rattlesnakes, for instance, secrete high levels of phospholipids in their venom. A rattlesnake bite therefore liquifies the interior of the prey and hastens digestion for the snake once it engulfs its victim.
Sphingomyelin Phosphodiesterase
An interesting "specialty" lipase is called sphingomyelin phosphodiesterase. The name of the lipase enzyme provides information about the specific kind of fat that the enzyme digests--in this case, sphingomyelin phosphodiester. These fats show up in animal cell membranes, and more specifically, in the myelin sheaths that insulate certain neurons, or nerve cells in the body. Explain Drs. Reginald Garrett and Charles Grisham in their text "Biochemistry," sphingomyelin helps nerves conduct impulses faster. Cells respond to certain forms of stress by breaking down sphingomyelin with the help of the enzyme sphingomyelin phosphodiesterase. Specifically, deficiency of the enzyme can lead to certain diseases, including Neimann-Pick disease.
References
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
- "Biochemistry"; Mary Campbell, Ph.D. and Shawn Farrell, Ph.D.; 2005
- "Biochemistry"; Reginald Garrett, Ph.D. and Charles Grisham, Ph.D.; 2007
