Porphobilinogen Deaminase: Involvement of stable covalent enzyme intermediate complexes in the enzyme from Rhodopseudomonas spheroides

1981 ◽  
Vol 9 (3) ◽  
pp. 231-232 ◽  
Author(s):  
ALAN BERRY ◽  
PETER M. JORDAN
Keyword(s):  
Porphobilinogen Deaminase ◽  
Rhodopseudomonas Spheroides ◽  
Enzyme Intermediate

scholarly journals Modification of hydroxymethylbilane synthase (porphobilinogen deaminase) by pyridoxal 5′-phosphate. Demonstration of an essential lysine residue

1984 ◽  
Vol 222 (1) ◽  
pp. 93-102 ◽  
Author(s):  
G J Hart ◽  
F J Leeper ◽  
A R Battersby
Keyword(s):  
Euglena Gracilis ◽  
Enzymic Activity ◽  
Lysine Residue ◽  
Porphobilinogen Deaminase ◽  
Amino Group ◽  
Spectroscopic Evidence ◽  
Lysine Residues ◽  
Modified Enzyme ◽  
Rhodopseudomonas Spheroides ◽  
Covalently Bound

When hydroxymethylbilane synthase (porphobilinogen deaminase) from Euglena gracilis is incubated with pyridoxal 5′-phosphate at pH 7.0 and 0 degree C, it rapidly loses part of its activity. The proportion of activity that remains decreases as the concentration of the modifier increases up to approx. 2mM, above which no further significant inactivation occurs. Dialysis of the partly inactivated enzyme restores its activity, whereas reduction with NaBH4 makes the inactivation permanent. The maximum inactivation achievable from one cycle of the treatment with pyridoxal 5′-phosphate, then with borohydride, is 53 +/- 5%; taking this modified enzyme through second and third cycles causes further loss of activity. The enzyme from Rhodopseudomonas spheroides behaves similarly, but there are quantitative differences. Spectroscopic evidence indicates that the inactivation procedure modifies lysine residues, and labelling studies show that epsilon-N-pyridoxyl-L-lysine is a product when permanently inactivated enzyme is completely hydrolysed. Several lysine residues per molecule of the E. gracilis enzyme are modified by the treatment with pyridoxal 5′-phosphate and borohydride, but only one appears to be essential for enzymic activity, since porphobilinogen protects the enzyme against inactivation and then one fewer lysine residue per molecule of enzyme is affected. It is suggested that, during the biosynthesis of hydroxymethylbilane, the first porphobilinogen unit is covalently bound to the enzyme through the epsilon-amino group of the essential lysine.

scholarly journals Mechanism of action of porphobilinogen deaminase. The participation of stable enzyme substrate covalent intermediates between porphobilinogen and the porphobilinogen deaminase from Rhodopseudomonas spheroides

1981 ◽  
Vol 195 (1) ◽  
pp. 177-181 ◽  
Author(s):  
P M Jordan ◽  
A Berry
Keyword(s):  
Mechanism Of Action ◽  
Catalytic Cycle ◽  
Porphobilinogen Deaminase ◽  
Enzyme Substrate ◽  
Enzyme Intermediates ◽  
Rhodopseudomonas Spheroides ◽  
Covalently Bound

Highly stable labelled complexes are formed between porphobilinogen deaminase and stoicheiometric amounts of [14C]porphobilinogen. On completion of the catalytic cycle by the addition of excess of substrate, the complexes yield labelled product and display all the properties expected from covalently bound enzyme intermediates involved in the deaminase catalytic sequence.

Urobiliverdin, a New Bile Pigment Deriving from Uroporphyrin

1983 ◽  
Vol 38 (9-10) ◽  
pp. 753-757 ◽  
Author(s):  
Eva Benedikt ◽  
Hans-Peter Köst
Keyword(s):  
Carboxylic Acid ◽  
Main Product ◽  
Aminolevulinic Acid ◽  
Chromic Acid ◽  
Bile Pigment ◽  
Enzyme Extract ◽  
Crude Enzyme Extract ◽  
Chromatographic Behaviour ◽  
Vis Spectroscopy ◽  
Rhodopseudomonas Spheroides

5-Aminolevulinic acid is incubated with a crude enzyme extract from Rhodopseudomonas spheroides, mutant R 26. The formed porphyrins (main product: uroporphyrin III) are isolated. Incorporation of iron, ring-splitting by coupled oxydation and subsequent iron removal leads to a mixture of pigments, from which urobiliverdin, a new bile pigment with eight carboxylic acid side chains, is isolated. It is characterized by its chromatographic behaviour, chromic acid degra­dation and UV-vis spectroscopy.

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