Proteolysis of a multienzyme conjugate: a possible mechanism for breaking a metabolic channel. [Neurospora]
The arom enzyme conjugate of Neurospora crassa is a polyfunctional protein that catalyzes five sequential reactions in the biosynthesis of the aromatic amino acids. Four of the five enzymes have been shown to be activated by the first substrate. In addition, evidence has been obtained in vivo and in vitro that the conjugate compartmentalizes and thereby channels its intermediate substrates. A third unique property observed for this enzyme system is that of coordinate protection by the conjugate's first substrate. All five activities are protected against proteolytic inactivation by the first substrate. Inactivation is essentially first-order, but in some instances it occurs only after a lag period. Selective inactivation of shikimate kinase, the most sensitive activity, is proposed as a regulatory mechanism that allows the cell to break the metabolic channel imposed by the conjugate in times of energy deficit. Such a break would allow the flow of carbon to be diverted from the energy-consuming aromatic amino acid biosynthetic pathway to an energy-yielding catabolic route.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- Sponsoring Organization:
- USDOE Environment and Safety
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 6037487
- Report Number(s):
- CONF-790456--1
- Country of Publication:
- United States
- Language:
- English
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Proteolytic inactivation and coordinate protection of the AROM enzyme conjugate of neurospora
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Related Subjects
550500 -- Metabolism
550700 -- Microbiology
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
AROMATICS
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL PATHWAYS
BIOSYNTHESIS
CARBOXYLIC ACIDS
CATABOLISM
CHEMICAL REACTIONS
DATA
DATA FORMS
DECOMPOSITION
ENERGY CONSUMPTION
ENZYME ACTIVITY
ENZYMES
EXPERIMENTAL DATA
FUNGI
GRAPHS
INACTIVATION
INFORMATION
ISOLATED VALUES
KINETICS
METABOLISM
NEUROSPORA
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
PHOSPHOTRANSFERASES
PLANTS
PROTEINS
PROTEOLYSIS
REACTION KINETICS
SUBSTRATES
SYNTHESIS
TRANSFERASES