Histidine determination

Langley, W. D. Urinary Histidine. Determination of Histidine in Urine. 

Frattini V, Lionetti C (1988) Histamine and histidine determination in tuna fish samples using high-performance liquid chromatography derivatization with o-phthalaldehyde and fluorescence detection or UV detection of free species. J Orromatogr A 809 241-245... 

Zhang, Z.-Y., Dixon, J. E. Active site labeling of the yersinia protein tyrosine phosphatase The determination of the pKa of active site cysteine and the function of the conserved histidine 402. Biochem. 32 (1993) 9340-9345. 

The results of experiments in which the mutation was made were, however, a complete surprise. The Asp 189-Lys mutant was totally inactive with both Asp and Glu substrates. It was, as expected, also inactive toward Lys and Arg substrates. The mutant was, however, catalytically active with Phe and Tyr substrates, with the same low turnover number as wild-type trypsin. On the other hand, it showed a more than 5000-fold increase in kcat/f m with Leu substrates over wild type. The three-dimensional structure of this interesting mutant has not yet been determined, but the structure of a related mutant Asp 189-His shows the histidine side chain in an unexpected position, buried inside the protein. 

The calibration of a and H12 is straightforward since tp1 and ip2 describe a proton transfer process and the relevant asymptotic points are easily determined using the pKa s of serine and histidine in water (see Chapter 5). The calibration of a 3 and A23 are more involved and require some effort in analyzing the available experimental information about AG 3 and Ag2 3 in water, which are considered below. 

The lipase (PAL) used in these studies is a hydrolase having the usual catalytic triad composed of aspartate, histidine, and serine [42] (Figure 2.6). Stereoselectivity is determined in the first step, which involves the formation of the oxyanion. Unfortunately, X-ray structural characterization of the (S)- and (J )-selective mutants are not available. However, consideration of the crystal structure of the WT lipase [42] is in itself illuminating. Surprisingly, it turned out that many of the mutants have amino acid exchanges remote from the active site [8,22,40]. 

Another example of noncysteinyl coordination of a [4Fe-4S] center was provided by the resolution of the X-ray structure of D. gigas hy-drogenase, which revealed that one iron atom of the distal [4Fe-4S] center was ligated by the atom of a histidine residue (164). Unfortunately, the EPR signature of this center could not be determined because of intercenter spin—spin interactions with other iron—sulfur centers (95). 

The X-ray structure of [cp Ir(CNR)Cl2], CNR = l,3,4,6-tetra-0-acetyl-2-deoxy-2-isocyano-Q,, 3-D-glucosc, has been determined.428 The synthesis of chiral complexes of Ir111 with Q-amino acid anions, L-L, of general formula [cp Ir(Cl)(L-L )] (252), and their NMR spectroscopic characterization, have been detailed. The X-ray structures of (252), L-L = L-proline and [cp Ir(Cl)(L-His-OH)]Cl, His = histidine, are described.429 C-allylglycinate binds in a terdentate manner in (253), which has been characterized by X-ray diffraction studies.430 C-vinylglycinate forms complex (254). 

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