Subsystem: Creatine and Creatinine Degradation

This subsystem's description is:

Creatine is a naturally occurring amino acid that is used to store and supply energy to muscle cells in vertebrates. Creatine is found in the blood, brain, and muscle of many organisms. The enzyme creatine kinase adds a phosphate to creatine (creatine + ATP = creatine-phosphate + ADP + 2 H+ ), generating creatine-phosphate (PCr).
Creatinine (Crn) is a breakdown product of creatine phosphate in muscle, and is usually produced at a fairly constant rate by the body in a nonenzymatic process. Creatinine is not reabsorbed, and is mainly filtered by the kidney and excreted in the urine. Both creatine and creatinine can be used by microorganisms as carbon and nitrogen sources.
In contrast to the nonenzymatic conversion of Cr and PCr to Crn in vertebrates, a growing number of microorganisms are being discovered to express specific enzymes for the degradation of Cr and Crn. Several lines of evidence suggest an involvement of microbial Cr and Crn degradation in vertebrate physiology and pathology. Bacteria and fungi capable of degrading Cr and Crn have been identified in chicken and pigeon droppings, human urine and feces , as well as the bacterial flora of the human colon.
At least four alternative microbial creatinine degradation pathways have been discovered (see Notes).

1.0 - Crn is degraded to 1-methylhydantoin and ammonia; a single enzyme displays both cytosine deaminase and Crn deaminase activity

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Literature ReferencesCreatine transporters: a reappraisal. Speer O Molecular and cellular biochemistry 2004 Jan-Feb14977199
Creatine and creatinine metabolism. Wyss M Physiological reviews 2000 Jul10893433
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