Biosynthesis of Heme and Chlorophyll Precursors

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; R o o t E n t r y F ÕwA C o m p O b j b W o r d D o c u m e n t O b j e c t P o o l wA wA 4 @ 0 1 2 3 4 5 6 7 8 9 : F Microsoft Word 6.0 Document MSWordDoc Word.Document.6 ; 9506901 Beale Tetrapyrrole pigments comprise a family of biomolecules including hemes, chlorophyll, bilins, and vitamin B12. These pigments function as essential components in the processes of respiration and photosynthesis, and also exist as cofactors in other important enzyme reactions. All tetrapyrroles arise from a branched biosynthetic pathway that has (-aminolevulinic acid (ALA) as its first committed member. The long term goals of this project are to understand the structure, mechanisms of action, and regulation of the enzymes that catalyze ALA formation in plants and algae, and how ALA formation controls the photosynthetic pigment content of these organisms. Efforts have recently been directed to exploiting the unique genetic and biochemical potentials of the unicellular alga Chlamydomonas reinhardtii to achieve these goals. Two light regulated genes have been cloned that encode enzymes which catalyze the formation and utilization of ALA, and these genes are being used to study enzyme mechanisms and regulation. It is proposed to isolate and purify the enzymes mf the ALA-forming pathway , to characterize their physical and kinetic properties, their cofactor requirements, their reaction mechanisms and possible enzyme interactions, to study the regulation of enzyme activity by allosteric modulators, and to determine changes in the enzyme abundance in response to light and cellular developmental status. Using cloned genes as molecular probes, cellular development processes, and mechanisms of regulation and expression of components of the chlorophyll biosynthetic pathway will be studied during adaptation of the cells to light. %%% Chlorophyll is the essential biological pigment which plants use to harvest sunlight for conversion into the biological energy that sustains all life on earth. The goals of this research project are to determine the biochemical reactions that plants employ to carry out the initial steps of chlorophyll formation, and to understand how plants control these reactions to achieve their ability to efficiently use the energy in sunlight. *** Oh +' 0 S u m m a r y I n f o r m a t i o n ( / $ H l D h R:\WWUSER\TEMPLATE\NORMAL.DOT METABOLIC BIOCHEMISTRY Shelley A. Graves Shelley A. Graves @ M wA @ @ M wA @ F # Microsoft Word 6.0 3 ; e = e j j j j j j j H # A 7 T L j j j j j ~ j j j j 9506901 Beale Tetrapyrrole pigments comprise a family of biomolecules including hemes, chlorophyll, bilins, and vitamin B12. These pigments function as essential components in the processes of respiration and photosynthesis, and also exist as cofactors in other important enzyme reactions. All tetrapyrroles arise from a branched biosynthetic pathway that has (-aminolevulinic acid (ALA) as its first committed member. The long term goals of this project are to understand the structure, mechanisms of action, and regulation of the enzymes that catalyze ALA formation in