Purification of glutamyl-tRNA reductase from Synechocystis sp. PCC 6803

Conference · Wed May 01 00:00:00 EDT 1991 · Plant Physiology, Supplement; (United States)

OSTI ID:5640503

Rieble, S; Beale, S I ^[1]

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1. Brown Univ., Providence, RI (United States)

{delta}-Aminolevulinic acid (ALA) is the universal precursor for all tetrapyrroles including hemes, chlorophylls, and bilins. In plants, algae, cyanobacteria, and many other bacteria, ALA is synthesized from glutamate in a reaction sequence that requires three enzymes, ATP, NADPH, and tRNA{sup Glu}. The three enzymes have been characterized as glutamyl-tRNA synthetase, glutamyl-tRNA reductase, and glutamate-1-semialdehyde (GSA) aminotransferase. All three enzymes have been separated and partially characterized from plants and algae. In prokaryotic phototrophs, only the glutamyl-tRNA synthetase and GSA aminotransferase have been described. The authors report here the purification and some properties of the glutamyl-tRNA reductase from extracts of the unicellular cyanobacterium, Synechocystis sp. PCC 6803. The glutamyl-tRNA reductase has been purified over 370 fold to apparent homogeneity. Its native molecular mass was determined to be 350 kDa by SDS-PAGE. The N-terminal amino acid sequence was determined for 42 residues. Much higher activity occurred with NADPH than with NADH as the reduced pyridine nucleotide substrate. Half-maximal rates occurred at 5 {mu}M NADPH, whereas saturation was not reached even at 10 mM NADH. Purified Synechocystis glutamyl-tRNA reductase was inhibited 50% by 5 {mu}M heme. Activity was unaffected by 10 {mu}M gabaculine. No flavin, pyridine nucleotide, or other light-absorbing prosthetic group was detected on the purified enzyme. The catalytic turnover number of purified Synechocystis glutamyl-tRNA reductase is comparable to those of prokaryotic and plastidic glutamyl-tRNA synthetases.

• OSTI ID: 5640503
• Report Number(s): CONF-9107184-; CODEN: PPYSA
• Journal Information: Plant Physiology, Supplement; (United States), Vol. 96:1; Conference: Annual meeting of the American Society of Plant Physiology, Albuquerque, NM (United States), 28 Jul - 1 Aug 1991; ISSN 0079-2241
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CYANOBACTERIA
ENZYME ACTIVITY
AMINO ACID SEQUENCE
AMINOLEVULINIC ACID
CATALYTIC EFFECTS
LIGASES
NAD
NADP
OXIDOREDUCTASES
AMINO ACIDS
CARBOXYLIC ACIDS
COENZYMES
ENZYMES
MICROORGANISMS
MOLECULAR STRUCTURE
NUCLEOTIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
PROTEINS
550200* - Biochemistry