Alternate mechanism for amino acid entry into Neurospora crassa: extracellular deamination and subsequent keto acid transport

DeBusk, R M; Brown, David T.; DeBusk, A. G.; Penderghast, R D

doi:10.1128/jb.146.1.163-169.1981

Cited by 14 publications

(12 citation statements)

References 33 publications

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“…Our conditions, however, required D-methionine to serve as the sole nitrogen source, which it may be ihcapable of doing and cannot, therefore, elicit a detectable enzyme level. Second, we previously reported an oxidase produced by the pmn; pmb; pmg strain in response to FPA under nitrogen-sufficient conditions (6). In contrast to the amino acid-induced activity, the FPA-induced activity was not nitrogen regulated.…”

Section: Methodsmentioning

confidence: 92%

“…Effect of the lox mutation on deaminase production. Extracellular deaminase activity can be produced in response to the amino acid analog FPA with an accompanying inhibition of growth due to deaminase conversion of FPA to its keto acid, which is then transported and regenerated as FPA (6). Ammonium was the nitrogen source for these earlier studies.…”

Section: Methodsmentioning

confidence: 99%

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Participation of an extracellular deaminase in amino acid utilization by Neurospora crassa

DeBusk¹,

Ogilvie²

1984

J Bacteriol

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A strain of Neurospora crassa defective in amino acid transport can utilize a variety of amino acids for growth when readily metabolizable nitrogen is limiting. Growth is accompanied by the production of an extracellular deaminase that converts the amino acid to its respective keto acid plus equimolar quantities of utilizable nitrogen in the ammonium ion form. Production of the deaminase is subject to ammonium repression. The relationship between the ability of an amino acid to trigger deaminase production and the presence of particular amino acid permease deficiencies is complex. Four classes of amino acids have been defined with respect to this relationship. The existence of multiple extracellular deaminases is discussed.

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Section: Methodsmentioning

confidence: 92%

Section: Methodsmentioning

confidence: 99%

Participation of an extracellular deaminase in amino acid utilization by Neurospora crassa

DeBusk¹,

Ogilvie²

1984

J Bacteriol

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“…The incorporation of 13 C relative to 15 N may also have been low as a result of the deamination of glycine by plant extracellular deaminases at the root surface. Although extracellular deaminases have not been localized on plant roots, they are present on other pho-tosynthetic organisms such as algae (Paul & Cooksey 1979DeBusk et al 1981). Hypothetically, their presence on the surface of roots could explain why 13 C incorporation was 50% lower than 15 N incorporation for excised roots of P. phryganodes incubated in sterile hydroponic media in short-term (20 min) 13 C 15 Nglycine uptake experiments (Henry & Jefferies 2003).…”

Section: Discussionmentioning

confidence: 99%

Plant amino acid uptake, soluble N turnover and microbial N capture in soils of a grazed Arctic salt marsh

Henry

Jefferies

2003

Journal of Ecology

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Summary 1The uptake of free amino acids by the grass Puccinellia phryganodes was investigated in soils of an Arctic coastal salt marsh, where low temperatures and high salinity limit inorganic nitrogen (N) availability, and the availability of soluble organic N relative to inorganic N is often high. N into plant roots and shoots were assessed. Chloroform fumigation-extraction was used to estimate the partitioning of labelled substrates into microbial biomass. 3 Free amino acids turned over rapidly in the soil, with half-lives ranging from 8.2 to 22.8 h for glycine and 8.9 to 25.2 h for leucine, compared with 5.6 to 14.7 h and 5.6 to 15.6 h for ammonium and nitrate, respectively. 15N from both organic and inorganic substrates was incorporated rapidly into plant tissue and the ratio of 13 C/ 15 N incorporation into plant tissue indicated that at least 5-11% of 13 C 15 N-glycine was absorbed intact. 4 Microbial C and N per unit soil volume were 1.7 and 5.4 times higher, respectively, than corresponding values for plant C and N. Plant incorporation of 15 N tracer was 56%, 83% and 68% of the comparable incorporation by soil microorganisms of glycine, ammonium and nitrate ions, respectively. 5 These results indicate that P. phryganodes can absorb amino acids intact from the soil despite competition from soil microorganisms, and that free amino acids may contribute substantially to N uptake in this important forage grass utilized by lesser snow geese in the coastal marsh.

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“…However, examination of roots under a light microscope showed no accumulation of slime on roots and no evidence of the build-up of bacterial plaque on the root surface under high magnification. In many algae and fungi, extracellular de-amination of amino acids can occur at the cell surface, followed by uptake of ammonium ions (Paul & Cooksey 1979, 1981DeBusk et al 1981;Munoz-Blanco, Hidalgo-Martínez & Cárdenas 1990). Although extracellular deaminases were not localized on the surface of root cell membranes, hypothetically, their presence could explain the low 13 C incorporation of 13 C 15 N-amino acids from hydroponic media.…”

Section: Discussionmentioning

confidence: 99%

Interactions in the uptake of amino acids, ammonium and nitrate ions in the Arctic salt‐marsh grass, Puccinellia phryganodes

Henry

Jefferies

2003

Plant Cell & Environment

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The uptake of amino acids and inorganic nitrogen by roots of Puccinellia phryganodes was examined to assess the potential contribution of soluble organic nitrogen to plant nitrogen uptake in Arctic coastal marshes, where free amino acids constitute a substantial fraction of the soilsoluble N pool. Short-term excised root uptake experiments were performed using tillers grown hydroponically under controlled conditions in the field. The percentage reductions in ammonium uptake at moderate salinity (150 m M NaCl) compared with uptake at low salinity (50 m M NaCl) were double those of glycine, but glycine uptake was more adversely affected than ammonium uptake by low temperatures. Glycine uptake was higher at pH 5·7 than at pH 7·0 or 8·2. The glycine uptake was upregulated in response to glycine, whereas ammonium uptake was up-regulated in response to ammonium starvation. Nitrate uptake was strongly down-regulated when tillers were grown on either ammonium or glycine. In contrast to N-starved roots, which absorbed ammonium ions more rapidly than glycine, the roots grown on glycine, ammonium and nitrate and not N-starved prior to uptake absorbed glycine as rapidly as ammonium and nitrate ions combined. Overall, the results indicate that amino acids are probably an important source of nitrogen for P. phryganodes in Arctic coastal marshes.

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Alternate mechanism for amino acid entry into Neurospora crassa: extracellular deamination and subsequent keto acid transport

Cited by 14 publications

References 33 publications

Participation of an extracellular deaminase in amino acid utilization by Neurospora crassa

Participation of an extracellular deaminase in amino acid utilization by Neurospora crassa

Plant amino acid uptake, soluble N turnover and microbial N capture in soils of a grazed Arctic salt marsh

Interactions in the uptake of amino acids, ammonium and nitrate ions in the Arctic salt‐marsh grass, Puccinellia phryganodes

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