Porphyrin biosynthesis in rhodopseudomonas palustris—II. Evidence on the existence of a factor regulating aminolevulinate synthetase activity

Alberto A Viale,Eva A.Wider De Xifra,Alcira M Del C Batlle

doi:10.1016/0020-711x(80)90153-6

Abstract

1. 1. No changes in ALA-S activity were observed when different preparations of R. palustris were stored at 4°C for various periods of time. 2. 2. Mixing supernatants from pigmented and decoloured R. palustris cells, showed that the activity of ALA-S was several times higher than expected, suggesting the presence of an activator. 3. 3. Supernatants from photosynthetically and aerobically grown cells were heated and the effect of the protein-free supernatant was tested on both red and white supernatants. The heated supernatant from aerobic cells increased ALA-S when added to red and white preparations, but the heated red supernatant only activated red supernatant and had no action on the white cells enzyme. 4. 4. By gel filtration on Sephadex G-25 of cell free extracts from R. palustris either aerobically or anaerobically grown, a low molecular weight compound was separated, which added back to the homologeous enzyme enhanced its activity confirming the existence of one or two low-molecular weight and heat-stable factors which would act stimulating ALA-S activity. 5. 5. A scheme is proposed to explain the role of these factors on the control of ALA-S in R. palustris.

Highlights

It is widely accepted that levels of Aminolevuhnic Acid (ALA) play a central role in the control of porphyrin biosynthesis in living systems
During early attempts to purify the enzyme from R. sphaeroides, variations in its activity were observed (Kikuchi et al, 1958b) and Aminolevulinate Synthetase (ALA-S) was resolved in two different iso-functional enzymes, a low activity and a high activity form (Tuboi & Hayasaka, 1972)
Interconversion of these forms has been shown to be dependent on the presence of certain thio-compounds and endogenous enzymes, suggesting that the activity of R. sphaeroides ALA-S might be controlled at a molecular level (Neubesges et al, 1973; Wider de Xifra et al, 1976)

Summary

OF A FACTOR REGULATING AMINOLEVULINATE SYNTHETASE ACTIVITY

BATLLE Centro de Investigaciones sobre Porfirinas y Porfirias-CIPYP, Fact&ad de Ciencias Exactas y Naturales. Universidad de Buenos Aires y Consejo National de Investigaciones Cientificas y T&micas-CONICET, Ciudad Universitaria, Pabellon If, 4to Piso. 3. Supernatants from photosynthetically and aerobically grown cells were heated and the effect of the protein-free supernatant was tested on both red and white supematants. The heated supernatant from aerobic cells increased ALA-S when added to red and white preparations, but the heated red supernatant only activated red supernatant and had no action on the white cells enzyme. 4. By gel filtration on Sephadex G-25 of cell free extracts from R. palustris either aerobically or anaerobically grown, a low molecular weight compound was separated, which added back to the homologeous enzyme enhanced its activity confirming the existence of one or two low-molecular weight and heat-stable factors which would act stimulating ALA-S activity. A scheme is proposed to explain the role of these factors on the control of ALA-S in R. palusrris

INTRODUCTION

MATERIALS AND MFITHODS

: RESULTS AND DKXXJSSION

Low MW fraction

Postulated scheme

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