Methionine degradation

Homocystinuria <0.5 Methionine degradation Cystathionine )8-synthase Faulty bone development mental retardation... 

Methionine Degradation Requires the Formation of a Key Methyl Donor, S-Adenosylmethionine... 

Lipid radical transfer has been demonstrated for trp, arg, his, and lys (99, 383, 384), all of which have reactive N groups on their side chains, and radical decomposition products from these amino acids have been identified (381, 382, 390). Tyrosine and methionine degradation by oxidizing lipids has also been demonstrated (390), but the intermediate radicals in the reaction may be too unstable for detection. Lipid radical adducts to amino acids are important flavor precursors (340) and also may play critical roles in pathological processes in vivo (186, 388). 

Methionine. Methionine degradation begins with the formation of S-adeno-sylmethionine, which is followed by a demethylation reaction, as described (Figure 14.16). S-Adenosylhomocysteine, the product of the latter reaction, is hydrolyzed to adenosine and homocysteine. Homocysteine then combines with serine to yield cystathionine. Cysteine, a-ketobutyrate, and NH4 result from... 

WAX fused silica capillaiy column (60 mx0.2S mm i.d. film thickness of 0.25 pm J W Scientific) was used. The operating conditions were as follows injector temperature, 250°C detector temperature, 250°C nitrogen carrier gas flow rate of 1.2 mL/min oven temperature program, 40°C (2 min), raised at 12°C/min to 210°C (20 min) 1 pL of sample was injected using a split ratio of 1 28. The amounts of the methionine degradation products were calculated by the ratios of the computed m eas versus that of the internal standard (methyl heptanoate). The response factors between the all degradation products and methyl heptanoate were determined in advance. 

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