Biochemistry and molecular biology of regulation of starch synthesis
Regulation of plant starch synthesis occurs at the level of ADPglc synthetase. 3-P-glycerate (3PGA) activates and P/sub i/ inhibits ADPG synthesis. 3PGA at high concentrations reverses P/sub i/ inhibition. Pyridoxal-P (PLP) activates the spinach leaf enzyme about 5- to 6-fold, but is not as effective as 3PGA which stimulates ADPglc synthesis 20-fold. PLP competes with 3PGA as an activator and reverses P/sub i/ inhibition thus suggesting that PLP binds at or close to the activator site. Reductive phosphopyridoxylation of the spinach leaf ADPglc synthetase with NaBH4 yields an enzyme with 5- to 6-fold higher activity in the absence of activator than the untreated enzyme when about 0.5 mol of (TH)-PLP is bound per mole of native enzyme. This modified enzyme is highly resistant to P/sub i/ inhibition in contrast to the treated enzyme. (TH)-PLP is incorporated into both 54 KD and 51 KD subunits of the enzyme. Incorporation into both peptides is inhibited by both 3PGA and P/sub i/. After incorporation of (TH)-PLP, the 51 KD subunit has been separated from the 54 KD subunit and subjected to tryptic digestion. A major radioactive peptide has been purified by HPLC and sequenced. The determined sequence was Ser-Gly-Ile-Val-Thr-Val-Ile-Lys-Asp-Ala-Leu-Ile-Pro-(Ser)- and is very similar to the deduced amino acid sequence obtained from a cDNA clone of the rice endosperm ADPglc synthetase gene. The amino acid sequence, the putative activator binding region, is situated near the C-terminus.
- Research Organization:
- Michigan State Univ., East Lansing
- OSTI ID:
- 6157199
- Report Number(s):
- CONF-870644-; TRN: 87-028646
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 46:6; Conference: 78. annual meeting of the American Society of Biological Chemists conference, Philadelphia, PA, USA, 7 Jun 1987
- Country of Publication:
- United States
- Language:
- English
Similar Records
Reexamination of the binding site for pyridoxal 5'-phosphate in ribulosebisphosphate carboxylase/oxygenase from Rhodospirillum rubrum
Phosphoenolpyruvate-dependent protein kinase enzyme I of Streptococcus faecalis: purification and properties of the enzyme and characterization of its active center
Related Subjects
LIGASES
ENZYME ACTIVITY
PEPTIDES
AMINO ACID SEQUENCE
STARCH
BIOSYNTHESIS
BIOCHEMISTRY
LIQUID COLUMN CHROMATOGRAPHY
MOLECULAR BIOLOGY
TRACER TECHNIQUES
TRITIUM COMPOUNDS
CARBOHYDRATES
CHEMISTRY
CHROMATOGRAPHY
ENZYMES
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
MOLECULAR STRUCTURE
ORGANIC COMPOUNDS
POLYSACCHARIDES
PROTEINS
REAGENTS
SACCHARIDES
SEPARATION PROCESSES
SYNTHESIS
550201* - Biochemistry- Tracer Techniques