Tyrosine analogs

Rachel, K., Asuncionpunzalan, E. and London, E. (1995) Anchoring of tryptophan and tyrosine analogs at the hydrocarbon polar boundary in model membrane-vesicles - paralax analysis of fluorescence quenching induced by nitroxide-labelled phospholipids. Biochemistry 34,15475-15479. 

We have used the nitration of a tyrosine analog with superoxide dismutase to measure the peroxynitrite production from activated rat alveolar macrophages (Fig. 38). The estimated rate of peroxynitrite synthesis was estimated to be 0.1 nmol/10 cells/min (Ischiropoulos et al., 1992a). The rate of nitration was the same whether native Cu,Zn-superoxide dismutase or the phenylglyoxyl-H202 modified superoxide dismutase (which is >99% inhibited with respect to its superoxide scavenging activity) was used (Fig. 39). Three other independent but indirect estimates of peroxynitrite formation were consistent with the superoxide... 

An orange-red color suggests the presence of hydroxylated tyrosine analogs (e.g.,... 

Bromination of a simple tyrosine analog, phloretic acid (p-hydroxy-phenylpropionic acid) (CIV), tvith two equivalents of reagent in aqueous... 

Figure 7.43. Conformationally constrained phenylalanine and tyrosine analogs.

No cross-reactivity has been seen with other nitro aromatics, such as nitro-phenylalanine, nitrotryptophan, or nitroguanine, nor with physiological tyrosine analogs such as phosphostyrosine, chlorotyrosine, dopamine, DOPA, dopamine, or tyramine (Ye et al., 1995). 

The intermediate 1 in the diagram is tyrosine. It is converted to DOPA ( 2 ). This rate-limiting step in catecholamine synthesis can be inhibited by the tyrosine analog metyrosine. The answer is (C). 

The hisT gene may also figure in the regulation of other metabolic pathways. Preliminary experiments indicate that the activity of the first enzyme in valine biosynthesis, acetohydroxy acid synthetase, is about five times as high in hisT mutants as it is in wild-type Salmonella [115]. Indirect evidence for the derepression of this pathway includes the excretion of valine by hisT mutants [115] and their resistance to the amino acid analogs trifluoroleucine and )S-hydroxyleucine [113]. The tyrosine pathway may also be affected in hisT mutants, since they are also resistant to the tyrosine analog aminotyrosine [113]. 

This methodology was apphed to synthesis of tyrosine analogs (Scheme 42). ... 

The majority of PET studies in oncology have been performed with C-labeled methionine, which is relatively easy to synthesize (41-43). Because of its low uptake in the brain, ["Cjmethionine has been proven to be a sensitive and specific tool for brain tumors, able to differentiate nonneoplastic from malignant lesions (42,44). Methionine uptake reflects the amino acid transport, whereas ["Cjtyrosine has been used to quantify protein synthesis rate in brain tumors (45,46). An I-iodinated tyrosine analog (IMT) also has been proposed to assess tumor cells proliferation by means of SPECT imaging. IMT uptake in glioma cells in vitro (47) and in soft-tissue sarcomas in vivo (48) was shown to be induced by rapid proliferation. 

Laws, W.R., Ross, J.B.A., Wyssbrod, H.R., Beechem, J.M., Brand, L., et al. Time-resolved fluorescence and H NMR studies of tyrosine and tyrosine analogs correlation of NMR-determined rotamer populations and fluorescence kinetics. Biochemistry 25, 599-607 (1986)... 

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