Pyridoxal phosphate absorption spectrum

The proton NMR spectrum of the coenzyme pyridoxal phosphate in 2HzO is shown in Fig. 3-24 as obtained with a 60-MHz spectrometer. Four things can be measured from such a spectrum (1) the intensity (area under the band). In a proton NMR spectrum, areas are usually proportional to the numbers of equivalent protons giving rise to absorption bands ... 

Figure 14-9 Absorption spectra of various forms of aspartate aminotransferase compared with that of free pyridoxal phosphate. The low pH form of the enzyme observed at pH <5 is converted to the high pH form with pka 6.3. Addition of erythro-3-hydroxyaspartate produces a quinonoid form whose spectrum here is shown only 1/3 its true height. The spectrum of free PLP at pH 8.3 is also shown. The...

Enzyme catalysis can be employed to detect concentrations of metabolites such as blood sugar, urea, uric acid or ATP. The metabolite is often best reacted with a co-enzyme such as NADPH or pyridoxal phosphate which changes its UV-vis absorption spectrum upon reaction. 

When purified, the DO PA decarboxylase of rat liver has an absorption spectrum similar to that of other pyridoxal-dependent enzymes. In this case, the co-enzyme seems to be very tightly bound to the apo-enzyme, but addition of an excess of pyridoxal phosphate still causes an increase in the enzyme activityii . It was therefore suggested that pyridoxal phosphate is a prosthetic group of this enzyme, and that when present in excess it acts as a co-enzyme. The 5-HTP decarboxylase of rat kidney was found to be potentiated by pyridoxal phosphate, but the effect was shown only when the tissue had been repeatedly frozen and thawed. These observations provide some evidence that pyridoxal phosphate is the co-enzyme for non-specific histidine decarboxylase. 

In close analogy to 3-hydroxypyridine, the chromophores in pyridoxamine phosphate and other related species of types 2 and 3 (Fig. 42) possessing a tetrsihedral centre at C-4, absorb at about 330 nm. The presence of an aldehyde function at this position, as in pyridoxal phosphate (Fig. 42, 1) shifts the absorption spectrum to 390 nm. The conversion of the aldehyde into a Schiff base is attended by a slight hypsochromic shift, but the protonation of the Schiff base produces a dramatic bathochromic shift and species of type 5 (Fig. 42) absorb at approximately 420-440 nm. Guided by the data from chemical model systems we examine the spectroscopic information obtained in the formation of binary and ternary complexes with several... 

Improvements in the procedure for purifying LAM, which included a more stringent adherence to anaerobicity, led to increased amounts of protein-bound iron, and allowed characterization of its configuration.LAM that is purified in an anaerobic chamber under conditions of less than 1 ppm of oxygen, normally contains 12-15 mol iron/mol hexamers, and exhibits a specific activity of 35-40 lU/mg, the maximum reported to date. The optical spectrum of the as-purified enzyme (Fig. 7) displays absorption features at 280 and 420 nm, a shoulder at 330 nm, and an additional broad feature that extends beyond 600 nm. These features indicate the presence of prosthetic groups in addition to pyridoxal 5 -phosphate, and are consistent with... 

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