Localization of constitutive phytases in lily pollen and properties of the pH 8 form

Baldi, Bruce G.; Scott, Jonathan J.; Everard, John D.; Loewus, Frank A.

doi:10.1016/0168-9452(88)90027-1

Cited by 37 publications

(31 citation statements)

References 32 publications

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“…Also, as seen in Figure 1, the final product of the reaction is IP 3 . Consistent with previous observations, further hydrolysis of IP 3 was not detected for an additional 48 h (Baldi, 1988).…”

Section: Resultssupporting

confidence: 81%

“…Attack adjacent to a free hydroxyl group could be due to greater nucleophilicity of the hydroxyl oxygen compared to the ester bond oxygen (Cosgrove, 1980b). The rates of removal of the second and third phosphates are significantly lower, possibly due to reduced specificity for I r 5 and IP4 (Baldi, 1988) and inhibition by the phosphate released. Altemative routes of hydrolysis of the intermediates leading to formation of multiple isomers of inositol phosphates were not observed.…”

Section: Discussionmentioning

confidence: 99%

“…Preparation of alkaline phytase followed the method of Baldi et al (1988). Lilium longiflorum L. cv Nellie White (1991 harvest) was kindly supplied by F.A.…”

Section: Preparation Of Alkaline Phytasementioning

confidence: 99%

“…Loewus (Scott and Loewus, 1986) isolated a new form of phytase from lily pollen that exhibits some unusual characteristics. It has a pH optimum of 8, it is not inhibited by fluoride at concentrations that inhibit acidic phytase activity by 90% (10 m), and it is activated by calcium ions (Baldi et al, 1988). Also, alkaline phytase removes only three phosphates from IP6 to yield IPS as the final product (Baldi et al, 1988;Loewus et al, 1990).…”

mentioning

confidence: 99%

“…It has a pH optimum of 8, it is not inhibited by fluoride at concentrations that inhibit acidic phytase activity by 90% (10 m), and it is activated by calcium ions (Baldi et al, 1988). Also, alkaline phytase removes only three phosphates from IP6 to yield IPS as the final product (Baldi et al, 1988;Loewus et al, 1990). More recently the presence of alkaline phytase in a variety of seeds was demonstrated (Scott, 1991).…”

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confidence: 99%

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Specificity of Hydrolysis of Phytic Acid by Alkaline Phytase from Lily Pollen

1994

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Phytases are the primary enzymes responsible for the hydrolysis of phytic acid, myo-inositol-1,2,3,4,5,6-hexakisphosphate (I-1,2,3,4,5,6-P,). A number of phytases with varying specificities, properties, and localizations hydrolyze phytic acid present in cells. l h e specificity of hydrolysis of phytic acid by alkaline phytase from lily (Lilium longiflorum 1.) pollen is described. Structures of the intermediate inositol phosphates and the final product were established by a variety of nuclear magnetic resonance techniques ('H-, 31P-, and 3'P-'H-detected multiple quantum coherence spectroscopy, and total correlation spectroscopy). O n the basis of the structures identified we have proposed a scheme of hydrolysis of phytic acid. Initial hydrolysis of the phosphate ester occurs at the D-5 position of phytic acid to yield the symmetrical I-1,2,3,4,6-P5. The two subsequent dephosphorylations occur adjacent to the D-5 hydroxyl group to yield I-1,2,3-P3 as the final product. Alkaline phytase differs from other phytases in the specificity of hydrolysis of phosphate esters on the inositol ring, its high substrate specificity for phytic acid, and biochemical properties such as susceptibility to activation by calcium and inhibition by fluoride. l h e physiological significance of alkaline phytase and the biological role of I-1,2,3-P3 remain to be identified.Phytic acid, myo-inositol hexakisphosphate, is a major constituent of seeds and pollen grains (1-5% of dry weight) (Loewus, 1990;Raboy, 1990). In mature lily (Lilium longiflorum L.) pollen and seeds, phytic acid is localized in membrane-bound phytic-rich granules. The presence of phytic acid in plant cells has been known for some time (Loewus, 1990;Raboy, 1990). However, it was only recently recognized that phytic acid is present in virtually all mammalian cells in concentrations higher than most other inositol phosphates (Menniti et al., 1993) and may function as a neurotransmitter (Vallejo et al., 1988). The discovery that I-1,4,5-P3 plays a crucial role in calcium cellular signaling (Bemdge et al., 1989) has greatly increased interest in the structure, metabolism, and biological role of inositol phosphates, including phytic acid.The primary enzymes responsible for the degradation of phytic acid are phytases. Phytases are a special class of phosphatases that catalyze the sequential hydrolysis of phytic acid to inositol phosphates and, in some cases, to inositol. Phytases occur in a variety of organisms including plants, fungi, and animals (reviewed by Cosgrove, 1980a). A variety of phytases differing in pH optima, substrate specificity, and * Corresponding author; fax 1-906-487-2061. specificity of hydrolysis have been identified in plants and fungi (Cosgrove, 1980a(Cosgrove, , 1980b. Acid phytases from wheat bran and Aspergilli have been extensively studied and the stereospecificity of hydrolysis has been well established (Cosgrove, 1980b). Based on the specificity of initial hydrolysis, two classes of acid phytases are recognized by the Intemational Union of Pure a...

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Section: Resultssupporting

confidence: 81%

Section: Discussionmentioning

confidence: 99%

“…Preparation of alkaline phytase followed the method of Baldi et al (1988). Lilium longiflorum L. cv Nellie White (1991 harvest) was kindly supplied by F.A.…”

Section: Preparation Of Alkaline Phytasementioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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