Cloning and expression of a new cDNA from monocotyledonous plants coding for a diadenosine 5′,5′′′‐P¹,P⁴‐tetraphosphate hydrolase from barley (Hordeum vulgare)

Abstract

From a cDNA library generated from mRNA of white leaf tissues of the ribosome‐deficient mutant ‘albostrians' of barley (Hordeum vulgare cv. Haisa) a cDNA was isolated carrying 54.2% identity to a recently published cDNA which codes for the diadenosine‐5′,5′′′‐P1,P4‐tetraphosphate (Ap4A) hydrolase of Lupinus angustifolius (Maksel et al. (1998) Biochem. J. 329, 313–319), and 69% identity to four partial peptide sequences of Ap4A hydrolase of tomato. Overexpression in Escherichia coli revealed a protein of about 19 kDa, which exhibited Ap4A hydrolase activity and cross‐reactivity with an antibody raised against a purified tomato Ap4A hydrolase (Feussner et al. (1996) Z. Naturforsch. 51c, 477–486). Expression studies showed an mRNA accumulation in all organs of a barley seedling. Possible functions of Ap4A hydrolase in plants will be discussed.

Schizosaccharomyces pombe Aps1, a Diadenosine 5‘,5‘ ‘‘-P1,P6-Hexaphosphate Hydrolase That Is a Member of the Nudix (MutT) Family of Hydrolases: Cloning of the Gene and Characterization of the Purified Enzyme,

“…Several nudix hydrolases are known to degrade Ap n A (n ) 3-6). Nudix hydrolases from human (5), pig (6), lupin (7), and barley (8) are classified as Ap 4 A hydrolases. A tomato Ap 4 A hydrolase, which has been partially sequenced and shows similarity to the human enzyme in the region of the signature motif, is probably a nudix hydrolase (9).…”

New Insight into Plant Signaling: Extracellular ATP and Uncommon Nucleotides

“…[156]. In plants, the activity of asymmetrical Np 4 N hydrolase was detected in Lupinus luteus seeds [157], Helianthus annuus and marrow (Cucurbita pepo) seeds [158], tomato cells [159], Lupinus angustifolius seeds [160] and in Hordeum vulgare [161]. Among Np 4 N's, only Ap 4 A can be degraded by the asymmetrical Np 4 N hydrolase giving ATP.…”