The interaction of pyridoxamine 5-phosphate with aspartate aminotransferase.
نویسندگان
چکیده
The binding of pyridoxamine 5-phosphate to the enzyme aspartate aminotransferase from pig heart was investigated by fluorescence spectroscopy. The substantial decrease in fluorescence intensity at 390 rnp that follows the interaction of pyridoxamine 5-phosphate with the apoenzyme was used to determine the alhnity constant. The effect of pH on the stability of the apoenzyme-pyridoxamine 5-phosphate complex was examined and it is shown that at neutral pH the complex is characterized by an association constant of 1.5 X lo7 M-‘. These studies provide information on the firmness of binding of pyridoxamine 5-phosphate to the active site on the enzyme.
منابع مشابه
Mechanism of binding of pyridoxamine 5-phosphate to the apoenzyme aspartate aminotransferase. Fluorescence studies.
The combination of pyridoxamine 5-phosphate with the apoprotein of the enzyme aspartate aminotransferase has been followed by measuring the quenching of protein fluorescence associated with complex formation. The reaction takes place in two steps; an initial rapid decrease in protein fluorescence is followed by a slow quenching process which parallels the recovery of catalytic activity. Similar...
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1. Acetylation of aspartate aminotransferase from pig heart inhibits completely the enzymic activity when the coenzyme is in the amino form (pyridoxamine phosphate) or when the coenzyme has been removed, but not when the coenzyme is in the aldehyde form (pyridoxal phosphate). 2. The group the acylation of which is responsible for the inhibition has been identified with the in-amino group of a l...
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The stereochemistry for hydrogen removal from pyridoxamine 5'-phosphate with liver pyridoxine (pyridoxamine)-5'-phosphate oxidase was examined to determine whether or not there are significant steric constraints at the substrate region of the active site of the oxidase. For this, pyridoxal 5'-phosphate was reduced with tritium-labeled sodium borohydride in ammoniacal solution to yield racemical...
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In previous studies it was found that: (a) aspartate aminotransferase increases the aspartate dehydrogenase activity of glutamate dehydrogenase; (b) the pyridoxamine-P form of this aminotransferase can form an enzyme-enzyme complex with glutamate dehydrogenase; and (c) the pyridoxamine-P form can be dehydrogenated to the pyridoxal-P form by glutamate dehydrogenase. It was therefore concluded (F...
متن کاملGlutamic-aspartic Transaminase. Reaction of Holoenzyme with Substrates and of Apoenzyme with Vitamin B6 Derivatives.
The general subject of enzymatic transamination has been extensively reviewed by several workers (Braunstein (I) ; Snell (2) ; Meister (3)). Glutamic-aspartic transaminase (L-aspartate : 2-oxoglutarate aminotransferase, EC 2.6.1.1) from pig heart. has been prepared by Jenkins, Yphantis, and Sizer (4) and shown to contain 2 molecules of pyridoxal phosphate per enzyme molecule of molecular weight...
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ورودعنوان ژورنال:
- The Journal of biological chemistry
دوره 244 1 شماره
صفحات -
تاریخ انتشار 1969