The purine nucleosidases of Jerusalem artichoke shoots

Floc'h, F. Le; Lafleuriel, J.

doi:10.1016/0031-9422(81)80098-2

Cited by 30 publications

(11 citation statements)

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“…1), the predicted masses of the ⌬L31M and ⌬I139M polypeptides, respectively. Notably, the specific activities of these purified preparations are 3 orders of magnitude higher than those previously reported for endogenous plant AMPD enzymes (120 -458 milliunits/mg of protein) (3,(11)(12)(13). The combined results demonstrate that up to 31 N-terminal amino acids in the FAC1 polypeptide are responsible for partitioning of the wild type enzyme into the particulate fraction.…”

Section: Expression and Purification Of Fac1 Recombinant Enzymes-fac1mentioning

confidence: 60%

“…The membrane association of FAC1 also explains why previous studies in pea seeds (3,10), spinach leaves (11), and artichoke tubers (7,12) were limited by the particulate nature of these enzymes, which resulted in poor purification yields that impeded further characterization. Baculoviral expression of FAC1 wild type cDNA also produces an enzyme that partitions (Ͼ95%) into the particulate fraction of an insect cell sonicate.…”

Section: Discussionmentioning

confidence: 98%

“…Asp 598 is located on ␤-strand 4 of the imperfect TIM barrel, where it appears to stabilize the N-␦ of His 659 located on the axial position of the catalytic zinc (Fig. 6A) Another unresolved issue relates to the well established observation that 2Ј-deoxy-AMP (dAMP) is not a good substrate for either plant or animal AMPD enzymes (2-16% rate of deamination relative to AMP) (11)(12)(13)48). This can be explained by an apparent interaction between Tyr 467 and the 2Ј-OH of coformycin 5Ј-phosphate that contributes to the different orientations of the ribose sugar and nitrogen base moieties of this transition state inhibitor in the active site of FAC1 (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Sequence analysis of available cDNA for the single A. thaliana gene (At2g38280) identifies motifs that could play structural and regulatory roles in plant-specific properties of AMPD. For example, a putative N-terminal helical transmembrane domain (residues 6 -31) may be responsible for the particulate distribution of plant enzymes, as reported in pea seeds (3,10), spinach leaves (11), and artichoke tubers (7,12). This behavior results in poor yields and impedes further purification efforts.…”

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confidence: 99%

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Membrane Association, Mechanism of Action, and Structure of Arabidopsis Embryonic Factor 1 (FAC1)

Han

Bingman

Mahnke

et al. 2006

Journal of Biological Chemistry

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Embryonic factor 1 (FAC1) is one of the earliest expressed plant genes and encodes an AMP deaminase (AMPD), which is also an identified herbicide target. This report identifies an N-terminal transmembrane domain in Arabidopsis FAC1, explores subcellular fractionation, and presents a 3.3-Å globular catalytic domain x-ray crystal structure with a bound herbicide-based transition state inhibitor that provides the first glimpse of a complete AMPD active site. FAC1 contains an (␣/␤) 8 -barrel characterized by loops in place of strands 5 and 6 that places it in a small subset of the amidohydrolase superfamily with imperfect folds. Unlike tetrameric animal orthologs, FAC1 is a dimer and each subunit contains an exposed Walker A motif that may be involved in the dramatic combined K m (25-80-fold lower) and V max (5-6-fold higher) activation by ATP. Normal mode analysis predicts a hinge motion that flattens basic surfaces on each monomer that flank the dimer interface, which suggests a reversible association between the FAC1 globular catalytic domain and intracellular membranes, with N-terminal transmembrane and disordered linker regions serving as the anchor and attachment to the globular catalytic domain, respectively.Embryonic factor 1 (FAC1) 5 was recently identified as one of the earliest expressed plant genes and is essential for the zygote to embryo transition in Arabidopsis thaliana (1). The zygote-lethal phenotype is characterized by developmental arrest at the 8 -16-cell stage and mutant embryo shriveling 2-3 days after fertilization. The Arabidopsis FAC1 locus encodes an AMP deaminase (AMPD; EC 3.5.4.6), which is a eukaryotic enzyme that catalyzes the hydrolytic deamination of AMP to IMP. AMPD has also been identified as the intracellular target for a class of herbicides that are produced by fungal pathogens. Carbocyclic coformycin was initially discovered in Saccharothrix (2), and plant cells can take up this diffusible nucleoside and 5Ј-phosphorylate it to produce a potent transition state inhibitor of AMPD (3). Exposure to carbocyclic coformycin results in cessation of seedling growth, followed by paling and necrosis at the apical meristem (3). Coformycin, a structurally related compound produced by a number of microbes (4, 5), also has herbicidal properties (5). Although the intracellular metabolism of this compound in plants has not been examined, its mode of action is presumably similar because coformycin 5Ј-phosphate is a transition state inhibitor of rabbit muscle AMPD (6). Both herbicides are inhibitors of mammalian adenosine deaminase (ADA) (3, 6), but the lack of this enzyme in plants (3, 7-9) supports the argument that AMPD is the intracellular target for their nucleotide derivatives. Taken together, these observations suggest that AMPD is essential throughout the plant life cycle. However, the underlying basis for lethality of a FAC1 null phenotype and for herbicidal toxicity related to the catalytic inhibition of this enzyme is not known.AMPD catalyzes the initial step in adenine to guanine ribon...

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Section: Expression and Purification Of Fac1 Recombinant Enzymes-fac1mentioning

confidence: 60%

Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Membrane Association, Mechanism of Action, and Structure of Arabidopsis Embryonic Factor 1 (FAC1)

Han

Bingman

Mahnke

et al. 2006

Journal of Biological Chemistry

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“…There are several biochemical studies on SAH hydrolase [3,19] and adenosine nucleosidase [17,20], but none on the subcellular localisation of these enzymes in leaves. Recently, genes encoding SAH hydrolase were cloned from tobacco [21] and parsley [22].…”

Section: Resultsmentioning

confidence: 99%

A new caffeine biosynthetic pathway in tea leaves: utilisation of adenosine released from the S‐adenosyl‐L‐methionine cycle

et al. 2001

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The four-step caffeine biosynthetic pathway includes three methylation steps that utilise S-adenosyl-L-methionine (SAM) as the methyl donor. In the process SAM is converted to S-adenosyl-L-homocysteine (SAH) which in turn is hydrolysed to L-homocysteine and adenosine. Significant amounts of radioactivity from [methyl-14 C]methionine and [methyl-14 C]SAM were incorporated into theobromine and caffeine in young tea leaf segments, and very high SAH hydrolase activity was found in cell-free extracts from young tea leaves. Substantial amounts of radioactivity from [adenosyl-14 C]SAH were also recovered as theobromine and caffeine in tea leaf segments, indicating that adenosine derived from SAH is utilised for the synthesis of the purine ring of caffeine. From the profiles of activity of related enzymes in tea leaf extracts, it is proposed that the major route from SAM to caffeine is a SAMC CSAHC CadenosineC CadenineC CAMPC CIMPC CXMPC CxanthosineC C7-methylxanthosineC C7-methylxanthineC CtheobromineC Ccaffeine pathway. In addition, direct adenosine kinase-catalysed formation of AMP from adenosine may participate as an alternative minor route. The activity of two of the three N-methyltransferase activities involved in caffeine biosynthesis and part of the activities of SAH hydrolase, adenosine nucleosidase, adenine phosphoribosyltransferase and adenosine kinase were located in tea chloroplasts. In contrast, no detectable activity of SAM synthetase was associated with the purified chloroplast fraction. This is a first demonstration that the purine skeleton of caffeine is synthesised from adenosine released from the SAM cycle. ß

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Interconversion of Purine Nucleotides

2020

Plant Nucleotide Metabolism ‐ Biosynthesis, Degradation, and Alkaloid Formation

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The purine nucleosidases of Jerusalem artichoke shoots

Cited by 30 publications

References 11 publications

Membrane Association, Mechanism of Action, and Structure of Arabidopsis Embryonic Factor 1 (FAC1)

Membrane Association, Mechanism of Action, and Structure of Arabidopsis Embryonic Factor 1 (FAC1)

A new caffeine biosynthetic pathway in tea leaves: utilisation of adenosine released from the S‐adenosyl‐L‐methionine cycle

Interconversion of Purine Nucleotides

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