Abstract

A dynamic mediatory role between starch synthesis and degradation has been ascribed to starch phosphorylase. However, plant starch phosphorylase is largely considered to be involved in phosphorolytic degradation of starch. It reversibly catalyzes the transfer of glucosyl units from glucose-1-phosphate to the non-reducing end of glucan chain with the release of inorganic phosphate. It is widely distributed in plant kingdom. Enzyme multiplicity is also common in starch phosphorylase and different multiple forms have been predicted to have different roles in starch metabolism. Here, various biochemical properties have been reviewed. Its regulation by aromatic amino acids has also been discussed. Importance of plastidial and cytoplasmic starch phosphorylase has also been discussed. Various biotechnological aspects have been discussed. Its exploitation in production of glucose-1-phosphate, a cytostatic compound has been discussed in the present review.

Key words: Starch phosphorylase, glucose-1-phosphate, amylase, biosensor, aromatic amino acids.

Abbreviation

Pi, orthophosphate; mRNA, messenger ribonucleic acid; Pho1,phosphorylase 1; Pho2, phosphorylase 2; KDa, kilodalton; Da, Dalton; P1, phosphorylase 1; P2, phosphorylase 2; P3, phosphorylase 3; L-form, light form; H-form, heavy form;ADPglucose, adenosine diphosphate glucose; L78, 78 amino acids long segment; Km,Michaelis constant; AMP, adenosine monophosphate; cAMP, 3’,5’-cyclic adenosine monophosphate; ATP, adenosine triphosphate; UDPglucose, uridine diphosphate glucose;GDPglucose, guanidine diphosphate glucose; NADP⁺, nicotinamide adenine dinucleotide;NADPH, reduced nicotinamide adenine dinucleotide; GT, glycosyl transferase; PEST-region,proline, glutamic acid, serine, threonine enriched region.