PMID: 6982150Jan 1, 1982Paper

On 4-hydroxyphenylpyruvate dioxygenase of adult frog liver

Comparative Biochemistry and Physiology. B, Comparative Biochemistry
S LindstedtM Rundgren

Abstract

1. It has been reported that 4-hydroxyphenylpyruvate dioxygenase (EC 1.13.11.27) activity in the liver from Rana esculenta is present only after autolysis of trypsin digestion, which releases a heat-and acid-stable inhibitor of low molecular mass. 2. Attempts to demonstrate similar effects with the liver enzyme from adult Rana pipiens were unsuccessful. Trypsin had only an inhibitory effect on the enzyme activity in crude extracts. 3. Both untreated and trypsin-treated enzyme had a molecular mass of about 100,000 daltons as determined by gel filtration. The pI was around pH 4.6. One pH-optimum between pH 7 and 8 was observed. 4. At pH 7.5 and 37 degrees C the basal enzyme activity was 1.3 mumol/min per g of protein. It was increased six-fold by a reductant in the presence of catalase. Fe2+ (50 muM) increased the activity further 1.6-fold when the reaction was carried out in Tris-HCl buffer, but not in potassium phosphate buffer. 5. The Km for 4-hydroxyphenylpyruvate was 50 muM and the Vmax was around 10 mumol/min per g of soluble protein with reductively activated enzyme. 6. Substrate inhibition was observed above 20 muM concentrations of 4-hydroxyphenylpyruvate.

References

Nov 17, 1975·Biochemical and Biophysical Research Communications·C NakaiO Hayaishi
Aug 1, 1971·Clinica Chimica Acta; International Journal of Clinical Chemistry·B Lindblad
Jun 10, 1961·Biochimica Et Biophysica Acta·M N GOSWAMI, W E KNOX
Jun 1, 1964·Biochimica Et Biophysica Acta·M N GOSWAMI

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