Nodulin-35: a subunit of specific uricase (uricase II) induced and localized in the uninfected cells of soybean nodules

The appearance of enzymes involved in the formation of ureides, allantoin, and allantoic acid, from inosine 5'-monophosphate was analyzed in developing root nodules of soybean (Glycine max). Concomitant with development of effective nodules, a substantial increase in specific activities of the enzymes 5'-nucleotidase (35-fold), purine nucleosidase (10-fold), xanthine dehydrogenase (25-fold), and uricase (200-fold), over root levels was observed. The specific activity of allantoinase remained constant during nodule development. With ineffective nodules the activities were generally lower than in effective nodules; however, the activities of 5'-nucleotidase and allantoinase were 2-fold higher in ineffective nodules unable to synthesize leghemoglobin than in effective nodules. Since the expression of uricase has been shown to be regulated by oxygen (K Larsen, BU Jochimsen 1986 EMBO J 5: 15-19), the expression of the remaining enzymes in the purine catabolic pathway were tested in response to variations in 02 concentration in sterile soybean callus tissue.

mentioning

confidence: 99%

“…One of the above enzymes, uricase, has been shown to be nodule-specific (3) and has been grouped as a class II nodulin.…”

mentioning

confidence: 99%

Appearance of Purine-Catabolizing Enzymes in Fix⁺ and Fix⁻ Root Nodules on Soybean and Effect of Oxygen on the Expression of the Enzymes in Callus Tissue

Larsen¹,

Jochimsen²

1987

“…On the other hand, uricase II and other enzymes of ureide metabolism have been detected in uninfected cells of soybean nodules (4). Specifically, uricase II has been localized within the peroxisomes of these cells (2,22). The enzyme uricase (Urate oxidase, EC 1.7.3.3.)…”

mentioning

confidence: 99%

Purification, cDNA Cloning, and Developmental Expression of the Nodule-Specific Uricase from Phaseolus vulgaris L.

Sánchez

Campos²,

Padilla³

et al. 1987

Nodule-specific uoricase (uricase I) from Phasolus vulgas L. was purified to homogeneity by chromatographic methods. Purification data indicated that uricas II is approximately 2% of the total soluble protein from mature nodules. Specific antiserum was raised and used to determine the developmental expression and for immunoselection of polysomes. Uricase II was antigenically detected early in nodule development, 2 to 3 days before nitrogen fixation. Uricase-encoding cDNA clones were isolated by hybridizing a nodule-specific pUC9 cDNA library with labeled mRNA from immunoselected polysomes and a 35,000 molecular weight uricase II-encoding cDNA from soybean. An homologous clone (pNF-UR07) was used to assess the expression pattern of the specific transcript during development. Northern-blot analysis indicated that uricase II mRNA is exclusively expressed in nodule tissue.

“…Also, the possible existence of apoferritin in normal Bradyrhizobium nodules may be subsequently elucidated. This latter aspect is particularly interesting because nodulin-35 (uricase II) is induced very early in nodule development, but significant uricase II activity is not detected until the commencement of nitrogen fixation (6). Thus, the 600 kD apoferritin, like nodulin-35, may undergo some modifications before it is activated to take up iron.…”

Section: Effects Of Bradyrhizobial/rhizobial Strains On the Presence Ofmentioning

confidence: 99%

The Occurrence of Phytoferritin and Its Relationship to Effectiveness of Soybean Nodules

Huang²,

Huang³

et al. 1987

Polyacrylamide gel electrophoresis and electron microscopy revealed that accumulation of iron-protein in soybean nodules is influenced by nodule age, mutation in bradyrhizobia, and rhizobial/bradyrhizobial strain-soybean cultivar interactions. Iron-protein stability, ultraviolet absorption spectrum, iron unloading and reloading, and characteristic appearance in electron micrographs. These properties led to the conclusion that the 570 kilodalton iron-protein is phytoferritin. The nodule phytoferritin differed from horse-spleen-ferritin in electrophoretic mobility, serological properties, and molecular size and was distinct from most other known phytoferritins in that it was composed of different subunit types.Phytoferritin is an iron-containing protein analogous to the ferritin found in mammalian cells (7,25). Accumulation of phytoferritin occurs primarily in nonphotosynthetic tissues functioning as a detoxicant against excess ferrous iron (7, 25). Phytofemtin also occurs in legume nodule meristems (5, 10 too small and too few to be utilized for biochemical studies. These difficulties could be overcome with the availability of nodule systems that accumulate large quantities of phytoferritin. The objectives of this study were to: (a) identify the factors influencing the accumulation of the iron-protein(s); (b) prove that the iron-protein is phytoferritin by its partial purification and characterization; and (c) establish a relationship between levels of phytoferritin and components of nitrogen fixation in nodules formed by bradyrhizobial/rhizobial mutants. MATERIALS AND METHODS