Changes in the patterns of phosphatase isozymes during the germination of rice seed

Suzuki, Shoho; Nisizawa, Kazutosi

doi:10.1007/bf02489060

Cited by 3 publications

(1 citation statement)

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“…Hence, the quantitative data on substrate specificity (Table IV) could not be verified electrophoretically. Phosphatases from the cereal grains almost always have high specificities toward ATP (10,13,21,22).…”

Section: Discussionmentioning

confidence: 99%

Some Properties of 3-Phosphoglycerate Phosphatase from Developing Rice Grain

Villareal¹,

Juliano²

1977

Plant Physiol.

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Some propewties of 3-P-glycerate phosphatase from developing caryopsis of rice (Oiyza sativa L., variety IR26) were studied. The enzyme was found to be soluble and not bound to starch, and concentrated mainly in the pericarp-aleurone layer; its maximum activity was at 12 to 14 days after flowering. Contents of 3-P-glycerate and chlorophyll were highest in the grain at 7 to 8 days after flowering when starch synthesis was at a maximum. The enzyme was purified about 100-fold by precipitation with 50 to 80% ammonium sulfate, followed by chromatography through Sephadex G-200 and CM-Sephadex C-50. The pH optimum was from 5.7 to 6 and no cation was required for activity. The purified preparation had an apparent Km of 2.85 mM and was inhibited by Cu2+, Hg2+, Zn2+, Fe3+, molybdate, and F-. The enzyme also exhibited high activity toward UTP, ATP, and p-nitrophenyl Grains were tagged at flowering and sampled in the mornings at specified intervals up to 21 days after flowering. These tagged grains were used as standards to classify periodic bulk samples used subsequently in the developmental study. The samples were dehulled and classified at 0 to 4 C. Duplicate batches of grains were analyzed at each developmental stages. For the study of enzyme distribution in the grain, samples at 9 to 10 days after flowering were dissected into their respective components: the hull, pericarp-aleurone layer, embryo, and endosperm. Statistical analyses were run on the data and LSD (5%) were calculated.Chemical Analysis. 3-P-Glycerate was extracted from freshly dehulled grains with 20% HCIO4 at 0 to 4 C and immediately assayed by the method of Latzko and Gibbs (1 1). Samples were taken in the mornings. Grains were dehulled directly from intact plants and the caryopses (dehulled grains) were immediately frozen in Dry Ice. Chlorophyll was also extracted from fresh grains by boiling 80% (v/v) aqueous acetone and was determined after Bruinsma (2). Soluble protein of the redissolved trichloroacetic acid precipitate (for the crude extract) and of the enzyme solutions (for the more purified fractions) was measured using the method of Lowry et al. (12).Enzyme Assay. 3-P-Glycerate phosphatase was assayed at 30 C with 10 Atmol sodium cacodylate buffer (pH 5.5) in a total volume of 1 ml. The reaction time was 15 min for the crude enzyme and 12 min for the more purified preparations. The reaction was terminated by adding 0.25 ml 10% trichloroacetic acid and the precipitate was removed by centrifuging at 2,500g for 15 min. Phosphate released was determined in the supernatant as described by Anderson and Tolbert (1).

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Section: Discussionmentioning

confidence: 99%