This binding causes a conformational change in the mRNA that can affect translational regulation often take action to manage an abundance of the instigating purine, and might produce proteins that facilitate purine metabolism or purine membrane uptake.
22.
In birds and reptiles, and in some desert dwelling mammals ( e . g ., the kangaroo rat ), uric acid also is the end-product of purine metabolism, but it is excreted in feces as a dry mass.
23.
For the treatment of rheumatoid arthritis, inhibition of DHFR is not thought to be the main mechanism, but rather multiple mechanisms appear to be involved, including the inhibition of enzymes involved in purine metabolism, leading to accumulation of adenosine; inhibition of T cell activation and suppression of intercellular adhesion molecule expression by T cells; selective down-regulation of B cells; increasing CD95 sensitivity of activated T cells; and inhibition of methyltransferase activity, leading to deactivation of enzyme activity relevant to immune system function.
24.
A compact graphical description of major biochemical reactions involved can be found at KEGG This provides information on the relevant enzymes and details the relationship with several other metabolic processes : glycine, serine, and threonine metabolism which provides hydroxypyruvate and glyoxylate, purine metabolism which provides glyoxylate, pyruvate metabolism which provides ( S )-malate and formate, carbon fixation which consumes 3-phospho-D-glycerate and provides D-ribulose 1, 5-P2, ascorbate and aldarate metabolism which shares tartronate-semialdehyde, nitrogen metabolism which shares formate, pyruvate metabolism and the citrate cycle which share oxaloacetate, and vitamin B 6 metabolism which consumes glycolaldehyde.
25.
"' 2, 5-diamino-6-hydroxy-4-( 5-phosphoribosylamino ) pyrimidine "'is a metabolite in the purine metabolism, formed by the hydrolysis of GTP by GTP cyclohydrolase II . Alternatively two separate enzymes can carry out this reaction, initially GTP cyclohydrolase IIa hydrolyses the 8, 9 bond to form 2-Amino-5-formylamino-6-( 5-phospho-D-ribosylamino ) pyrimidin-4 ( 3H )-one, followed by de-formylation by 2-amino-5-formylamino-6-ribosylaminopyrimidin-4 ( 3H )-one 5'- monophosphate deformylase . 2, 5-diamino-6-hydroxy-4-( 5-phosphoribosylamino ) pyrimidine is deaminated by Diaminohydroxyphosphoribosylaminopyrimidine deaminase to form 5-amino-6-( 5-phosphoribosylamino ) uracil.
