Kinetic and molecular parameters of human hepatic porphobilinogen deaminase.
A basal level of human liver porphobilinogen deaminase of 3.66 units/g wet weight was found in adult tissue. Activity in neonatal liver was at least three fold higher. Physico-chemical studies revealed that the enzyme has the approximate form of a symmetrical molecule and exhibits hyperbolic kinetics with a Km value of 3.6 microM at pH 7.6. Two ionizable groups with pK values of 7.35 and 8.90 are prominent for catalysis. A set of pI (5.8-4.9) were observed under different conditions. Results demonstrate the existence of a single protein differentially charged with multiple molecular forms in adult liver.
Mazzetti
M B
MB
Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
Tomio
J M
JM
D000328:Adult; D006801:Humans; D006863:Hydrogen-Ion Concentration; D011163:Hydroxymethylbilane Synthase / Q000737:chemistry / Q000378:metabolism*; D007231:Infant, Newborn; D007525:Isoelectric Focusing; D007700:Kinetics; D008099:Liver / Q000201:enzymology*
D011163:Hydroxymethylbilane Synthase