Biomedical subjects

U Kikkawa

Publications and source records attributed to U Kikkawa.

At least 19 recordsLinked to original sources

PubMed2001

UV-induced tyrosine phosphorylation of PKC delta and promotion of apoptosis in the HaCaT cell line.

Protein kinase C delta (PKC delta) is activated through tyrosine phosphorylation and is involved in apoptosis induction in the H(2)O(2)-treated fibroblasts. In the human keratinocyte HaCaT cell line, ultraviolet radiation, which induces apoptosis, promoted tyrosine phosphorylation and activation of PKC delta, but neither enhanced threonine phosphorylation in the activation loop nor generated the catalytic fragment of the PKC isoform. Tyrosine phosphorylation of PKC delta was prevented by a radical scavenger, N-acetyl-l-cysteine, and by a tyrosine kinase inhibitor, genistein, in the ultraviolet-irradiated keratinocyte cell line. Ultraviolet radiation-induced apoptosis was attenuated by N-acetyl-l-cysteine and genistein as well as by a PKC inhibitor, bisindolylmaleimide I. These results indicate that reactive oxygen species generated by ultraviolet radiation enhance tyrosine phosphorylation of PKC delta, and the PKC isoform thus activated by the modification reaction contributes to induction of apoptotic cell death in keratinocytes.

Antineoplastic Agents↗

PubMed2001

Phosphorylation sites of protein kinase C delta in H2O2-treated cells and its activation by tyrosine kinase in vitro.

Protein kinase C delta (PKC delta) is normally activated by diacylglycerol produced from receptor-mediated hydrolysis of inositol phospholipids. On stimulation of cells with H(2)O(2), the enzyme is tyrosine phosphorylated, with a concomitant increase in enzymatic activity. This activation does not appear to accompany its translocation to membranes. In the present study, the tyrosine phosphorylation sites of PKC delta in the H(2)O(2)-treated cells were identified as Tyr-311, Tyr-332, and Tyr-512 by mass spectrometric analysis with the use of the precursor-scan method and by immunoblot analysis with the use of phosphorylation site-specific antibodies. Tyr-311 was the predominant modification site among them. In an in vitro study, phosphorylation at this site by Lck, a non-receptor-type tyrosine kinase, enhanced the basal enzymatic activity and elevated its maximal velocity in the presence of diacylglycerol. The mutation of Tyr-311 to phenylalanine prevented the increase in this maximal activity, but replacement of the other two tyrosine residues did not block such an effect. The results indicate that phosphorylation at Tyr-311 between the regulatory and catalytic domains is a critical step for generation of the active PKC delta in response to H(2)O(2).

Amino Acid Sequence↗

PubMed2001

Toward the identification of selective modulators of protein kinase C (PKC) isozymes: establishment of a binding assay for PKC isozymes using synthetic C1 peptide receptors and identification of the critical residues involved in the phorbol ester binding.

Conventional and novel protein kinase C (PKC) isozymes contain two cysteine-rich C1 domains (C1A and C1B), both of which are candidate phorbol-12,13-dibutyrate (PDBu) binding sites. We previously synthesized C1 peptides (of approximately 50 residues) corresponding to all PKC isozymes and measured their PDBu binding affinity. While many of these peptide receptors exhibited PDBu affinities comparable to the respective complete isozyme, some of the C1A peptides could not be used because they undergo temperature dependent inactivation. This problem was however eliminated by 4 degrees C incubation or elongation of the 50-mer C1 peptides at both N- and C-termini to increase their folding efficiency and stability. These findings enabled us to determine the K(d)'s of PDBu for all PKC C1 peptides (except for theta-C1A) and establish the value of these peptides as readily available, stable, and easily handled surrogates of the individual isozymes. The resultant C1 peptide receptor library can be used to screen for new ligands with PKC isozyme and importantly C1 domain selectivity. Most of the C1 peptide receptors showed strong PDBu binding affinities with K(d)'s in the nanomolar range (0.45-7.4 nM). Two peptides (delta-C1A and theta-C1A) bound PDBu over 100-fold less tightly. To identify the residues that contribute to this affinity difference, several mutants of delta-C1A and theta-C1A were synthesized. Both the G9K mutant of delta-C1A and the P9K mutant of theta-C1A showed K(d)'s of 2-3 nM. This approach provides a useful procedure to determine the role of each C1 domain of the PKC isozymes by point mutation.

Amino Acid Sequence↗

PubMed2001

Involvement of the phosphoinositide 3-kinase/protein kinase B signaling pathway in insulin/IGF-I-induced chondrogenesis of the mouse embryonal carcinoma-derived cell line ATDC5.

The embryonal carcinoma-derived cell line, ATDC5, differentiates into chondrocytes in response to insulin/insulin-like growth factor-I (IGF-I) stimulation. In the present study, we examined whether insulin/IGF-I stimulation caused activation of the phosphoinositide 3-kinase (PI3K)/protein kinase B (PKB) pathway in ATDC5 cells. We also determined whether the insulin-stimulated differentiation of ATDC5 cells into chondrocytes could be mimicked by activation of the PKB pathway alone. ATDC5 cells produced phosphatidylinositol 3,4,5-trisphosphate and the pleckstrin homology domain of PKB was recruited to the plasma membrane in response to insulin stimulation. This was probably a result of activation of PI3K because the PI3K inhibitors, wortmannin and LY294002, inhibited both responses, although the effective concentrations were as high as 10 microM. Insulin stimulation caused the chondrogenic differentiation of ATDC5 cells as assessed by chondrogenic nodule staining with alcian blue. The addition of wortmannin or LY294002, PI3K inhibitors, suppressed the staining, and the suppression was reversible, indicating the effect of the inhibitors is not toxic. Finally, we exogenously expressed a constitutively-activated from of PKB (myristoylated PKB, myr-PKB) in ATDC5 cells, and found the chondrogenic differentiation of ATDC5 cells to form nodules occurred in the absence of insulin stimulation. The kinase-negative mutant of myr-PKB did not caused differentiation, indicating that kinase activity is required. These results support the hypothesis that the PI3K/PKB signaling pathway is involved in the chondrogenic differentiation of ATDC5 cells in response to insulin/IGF-I stimulation. This is the first report that demonstrates the involvement of phosphoinositide signaling in the induction of chondrogenesis from undifferentiated cells.

Androstadienes↗

PubMed2000

Akt-dependent cytokine production in mast cells.

Cross-linking of FcepsilonRI induces the activation of three protein tyrosine kinases, Lyn, Syk, and Bruton's tyrosine kinase (Btk), leading to the secretion of a panel of proinflammatory mediators from mast cells. This study showed phosphorylation at Ser-473 and enzymatic activation of Akt/protein kinase B, the crucial survival kinase, upon FcepsilonRI stimulation in mouse mast cells. Phosphorylation of Akt is regulated positively by Btk and Syk and negatively by Lyn. Akt in turn can regulate positively the transcriptional activity of interleukin (IL)-2 and tumor necrosis factor (TNF)-alpha promoters. Transcription from the nuclear factor kappaB (NF-kappaB), nuclear factor of activated T cells (NF-AT), and activator protein 1 (AP-1) sites within these promoters is under the control of Akt activity. Accordingly, the signaling pathway involving IkappaB-alpha, a cytoplasmic protein that binds NF-kappaB and inhibits its nuclear translocation, appears to be regulated by Akt in mast cells. Catalytic activity of glycogen synthase kinase (GSK)-3beta, a serine/threonine kinase that phosphorylates NF-AT and promotes its nuclear export, seems to be inhibited by Akt. Importantly, Akt regulates the production and secretion of IL-2 and TNF-alpha in FcepsilonRI-stimulated mast cells. Altogether, these results revealed a novel function of Akt in transcriptional activation of cytokine genes via NF-kappaB, NF-AT, and AP-1 that contributes to the production of cytokines.

Animals↗

PubMed2000

H(2)O(2)-induced tyrosine phosphorylation of protein kinase cdelta by a mechanism independent of inhibition of protein-tyrosine phosphatase in CHO and COS-7 cells.

It has been proposed that H(2)O(2) increases tyrosine phosphorylation of cellular proteins by inhibiting protein-tyrosine phosphatase through oxidation of the cysteine residue of the enzyme essential for its catalytic activity. Tyrosine phosphorylation of the delta isoform of protein kinase C (PKC) was induced by H(2)O(2) in CHO and COS-7 cells. H(2)O(2) also induced activation of mitogen-activated protein kinase. Vanadate and molybdate, which inhibit protein-tyrosine phosphatase by binding to its active site, did not induce tyrosine phosphorylation of PKCdelta, but enhanced H(2)O(2)-induced tyrosine phosphorylation of PKCdelta in the cell. The oxoanions, however, generated the active form of mitogen-activated protein kinase. Another protein-tyrosine phosphatase inhibitor, phenylarsine oxide, which bridges the thiol residues of the enzyme, induced tyrosine phosphorylation of PKCdelta, and the reaction was enhanced by vanadate. These results suggest that inhibition of protein-tyrosine phosphatase is insufficient for induction of tyrosine phosphorylation of PKCdelta in the cells, and that presumably activation of protein-tyrosine kinase may be essential for tyrosine phosphorylation of the PKC isoform.

3T3 Cells↗

PubMed2000

Immunocytochemical localization of a neuron-specific thrombospondin-1-like protein, NELL2: light and electron microscopic studies in the rat brain.

We have studied the cellular and intracellular localization of NELL2, a neural thrombospondin-1-like protein. NELL2 protein was detected as doublet bands of 140 and 90 kDa with the use of the specific antibodies raised against the C-terminal region of NELL2 and was recognized only in the brain but not in the peripheral tissues. Within the brain, NELL2 was abundantly present in the hippocampus and cerebral cortex, found moderately in the olfactory bulb and hypothalamus, and at a low level in the thalamus, cerebellum, and medulla. Immunocytochemically, NELL2 was seen only in neurons but not in glial cells or in the white matter. NELL2-immunoreactive cells were distributed throughout the brain with the highest density in the hippocampus and cerebral cortex. NELL2 was mainly found in the cell bodies of neurons and the immunoreactivity was often seen as dots in the perikarya. The distribution of NELL2 immunoreactivity did not completely correspond to that of any subtypes of protein kinase C (PKC). Under electron microscopy, NELL2 protein was associated with the endoplasmic reticulum (ER), especially with rough ER. NELL2 immunoreactivity was found in the restricted parts of the ER and found commonly inside the ER. These results suggest that NELL2 protein is synthesized by neurons and may be secreted from the neurons involved in certain neuronal functions.

Animals↗

PubMed2000

Regulation of melanogenesis through phosphatidylinositol 3-kinase-Akt pathway in human G361 melanoma cells.

The involvement of the phosphatidylinositol 3-kinase pathway in the regulation of melanogenesis was examined using human G361 melanoma cells. In the cells treated with wortmannin, a potent inhibitor of phosphatidylinositol 3-kinase, the melanin content increased concomitant with the elevated protein level of tyrosinase, a key enzyme in melanogenesis. Northern blot analysis revealed that the mRNA level of tyrosinase increased transiently on treatment of the cells with the phosphatidylinositol 3-kinase inhibitor. When the cells were infected with the adenovirus vector encoding the mutant adapter subunit of phosphatidylinositol 3-kinase, which acts as a dominant negative of phosphatidylinositol 3-kinase, both the melanin content and the expression of tyrosinase increased. In cells infected with the adenovirus vector encoding the constitutively active mutant of the lipid kinase, a decrease in melanin content as well as reduced expression of tyrosinase was observed. In cells expressing the constitutively active mutant of the serine-threonine protein kinase Akt, one of the downstream targets of phosphatidylinositol 3-kinase, the melanin content decreased as in the cells overproducing the constitutively active mutant of phosphatidylinositol 3-kinase. These results indicate that phosphatidylinositol 3-kinase regulates melanogenesis by modulating the expression of tyrosinase, and that activation of Akt is sufficient for suppression of melanin production in G361 melanoma cells.

Androstadienes↗

PubMed2000

Studies on the phosphorylation of protein kinase B by Ca(2+)/calmodulin-dependent protein kinases.

Protein kinase B (PKB) was recently reported to be activated on the phosphorylation of Thr(308) by Ca(2+)/calmodulin-dependent protein kinase kinase alpha (CaM-kinase kinase alpha), suggesting that PKB was regulated through not only the phosphoinositide 3-kinase pathway but also the Ca(2+)/calmodulin protein kinase pathway. The activation of PKB by CaM-kinase kinase alpha was as high as 300-fold after incubation for 30 min under the phosphorylation conditions, and still increased thereafter, suggesting that the maximal activation of PKB on phosphorylation of the Thr(308) residue is several hundred fold. On the other hand, the V(max) value of CaM-kinase kinase alpha for the phosphorylation of PKB was more than two orders of magnitude lower than that for CaM-kinase IV, although the K(m) values for PKB and CaM-kinase IV were not significantly different, raising the question of whether or not PKB is a physiological substrate of CaM-kinase kinase alpha. Besides CaM-kinase kinase alpha, CaM-kinase II also remarkably activated PKB. However, the specific activities of CaM-kinase kinase alpha and CaM-kinase II as to the activation of PKB were more than three orders of magnitude lower than that of 3-phosphoinositide-dependent protein kinase 1 (PDK1).

Animals↗

PubMed1999

Opposing effects of protein kinase C delta and protein kinase B alpha on H(2)O(2)-induced apoptosis in CHO cells.

H(2)O(2)-induced apoptosis was enhanced in the CHO cell line overproducing protein kinase C delta (PKCdelta) as judged by DNA fragmentation. In response to the H(2)O(2) treatment, PKCdelta was tyrosine phosphorylated and recovered as a constitutively active form, but its proteolytic fragment was not generated. In contrast, H(2)O(2)-induced apoptosis was suppressed in the CHO cell line overexpressing protein kinase B alpha (PKBalpha). Consistently, phosphorylation of BAD, a pro-apoptotic protein negatively regulated by PKBalpha, was sustained in the cells overproducing PKBalpha, but was not changed in the cells overexpressing PKCdelta. In the CHO cell line overproducing both PKCdelta and PKBalpha, H(2)O(2)-induced tyrosine phosphorylation of PKCdelta was suppressed, and DNA fragmentation was diminished concomitantly. These results suggest that PKCdelta contributes to H(2)O(2)-induced apoptosis by a mechanism independent of BAD and that PKCdelta is a target of PKB for the regulation of cell survival.

Animals↗

PubMed1999

Akt phosphorylation site found in human caspase-9 is absent in mouse caspase-9.

Caspase-9 is one caspase upstream of caspase-3 and its activation is stimulated by Apaf-1/cytochrome c and inhibited by Akt signals. BAD phosphorylation by Akt is an essential step for growth factor-mediated inhibition of caspase activation. Recently, it was shown that human caspase-9 is phosphorylated by Akt and that its protease activity is reduced. To clarify the molecular mechanism of regulation of caspase-9 activation in neuronal apoptosis, we isolated two alternative splicing products of mouse caspase-9, caspase-9L and caspase-9S, from a P19 embryonal carcinoma cell cDNA library. Curiously, the Akt phosphorylation sites and motifs found in human caspase-9 were absent in both mouse caspase-9L and -9S. Mouse caspase-9 was not phosphorylated by activated Akt in vitro. Reverse transcription polymerase chain reaction analysis showed that the absent Akt motif is not limited to caspase-9 expressed in P19 embryonal carcinoma cells but also occurs in caspase-9 expressed in mouse, rat, and monkey. These results suggest that inhibition of caspase-9 activation by Akt-dependent phosphorylation is not generalized across species.

Amino Acid Sequence↗

PubMed1999

Regulation of nuclear translocation of forkhead transcription factor AFX by protein kinase B.

The regulation of intracellular localization of AFX, a human Forkhead transcription factor, was studied. AFX was recovered as a phosphoprotein from transfected COS-7 cells growing in the presence of FBS, and the phosphorylation was eliminated by wortmannin, a potent inhibitor of phosphatidylinositol (PI) 3-kinase. AFX was phosphorylated in vitro by protein kinase B (PKB), a downstream target of PI 3-kinase, but a mutant protein in which three putative phosphorylation sites of PKB had been replaced by Ala was not recognized by PKB. In Chinese hamster ovary cells (CHO-K1) cultured with serum, the AFX protein fused with green fluorescence protein (AFX-GFP) is localized mainly in the cytoplasm, and wortmannin induced transient nuclear translocation of the fusion protein. The AFX-GFP mutant in which all three phosphorylation sites had been replaced by Ala was detected exclusively in the cell nucleus. AFX-GFP was in the nucleus when the cells were infected with an adenovirus vector encoding a dominant-negative form of either PI 3-kinase or PKB, whereas the fusion protein stayed in the cytoplasm when the cells expressed constitutively active PKB. In CHO-K1 cells expressing AFX-GFP, DNA fragmentation was induced by the stable PI 3-kinase inhibitor LY294002, and the expression of the active form of PKB suppressed this DNA fragmentation. The phosphorylation site mutant of AFX-GFP enhanced DNA fragmentation irrespective of the presence and absence of PI 3-kinase inhibitor. These results indicate that the nuclear translocation of AFX is negatively regulated through its phosphorylation by PKB.

Animals↗

PubMed1999

Involvement of EF hand motifs in the Ca(2+)-dependent binding of the pleckstrin homology domain to phosphoinositides.

The pleckstrin homology (PH) domains of phospholipase C (PLC)-delta1 and a related catalytically inactive protein, p130, both bind inositol phosphates and inositol lipids. The binding to phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] by PLC-delta1 is proposed to be the critical interaction required for membrane localization to where the substrate resides; it is also required for the Ca(2+)-dependent activation of PLC-delta1 observed in the permeabilized cells. In the proximity of the PH domain, both PLC-delta1 and p130 possess the EF-hand domain, containing classical motifs implicated in calcium binding. Therefore, in the present study we examined whether the binding of the PH domain to PtdIns(4,5)P2 is regulated by changes in free Ca2+ concentration within the physiological range. A Ca2+ dependent increase in the binding to PtdIns(4,5)P2 was observed with a full-length PLC-delta1, while the isolated PH domain did not show any Ca2+ dependence. However, the connection of the EF-hand motifs to the PH domain restored the Ca2+ dependent increase in binding, even in the absence of the C2 domain. The p130 protein showed similar properties to PLC-delta1, and the EF-hand motifs were again required for the PH domain to exhibit a Ca2+ dependent increase in the binding to PtdIns(4,5)P2. The isolated PH domains from several other proteins which have been demonstrated to bind PtdIns(4,5)P2 showed no Ca2+ dependent enhancement of binding. However, when present within a chimera also containing PLC-delta1 EF-hand motifs, the Ca2+ dependent binding was again observed. These results suggest that the binding of Ca2+ to the EF-hand motifs can modulate binding to PtdIns(4,5)P2 mediated by the PH domain.

Blood Proteins↗

PubMed1999

Synthesis and phorbol ester-binding studies of the individual cysteine-rich motifs of protein kinase D.

To investigate the phorbol ester-binding properties of the individual cysteine-rich motifs of protein kinase D (PKD), the 52-mer peptides containing each cysteine-rich motif of PKD (PKD-C1A, PKD-C1B) have been synthesized. The [3H]phorbol-12,13-dibutyrate (PDBu) binding to PKD-C1A was affected drastically by incubation temperature while that to PKD-C1B was not. Scatchard analysis of [3H]PDBu binding to both PKD C1 peptides gave dissociation constants of 2.5 +/- 0.4 and 2.7 +/- 0.8 nM for PKD-C1A and PKD-C1B, respectively, indicating that the two cysteine-rich motifs of PKD are functionally equivalent like those of PKCgamma.

Amino Acid Sequence↗

PubMed1999

Identification of the catalytic subunit of cAMP-dependent protein kinase from the photosynthetic flagellate, Euglena gracilis Z.

A gene named epk2 that encodes the amino acid sequence of a protein kinase was identified from the photosynthetic flagellate, Euglena gracilis Z. Homology search and phylogenetic analysis revealed that the deduced amino acid sequence of epk2 is most similar to that of the catalytic subunit of cAMP-dependent protein kinase (PKA). Northern blot analysis showed that Euglena cells express a 1.4-kb transcript of this gene. When the EPK2 protein was coexpressed with the rat regulatory subunit of PKA in cultured mammalian cells, these two proteins were coimmunoprecipitated. The association of EPK2 and the rat regulatory subunit of PKA was not detected in the cell lysate incubated with cAMP. EPK2 immunoprecipitated from the transfected cells phosphorylated Kemptide, a synthetic peptide substrate for PKA, and the phosphorylation was inhibited by PKI, a PKA-selective protein kinase inhibitor. These results indicate that EPK2 is a PKA homologue in the photosynthetic flagellate, and this is the first evidence for the occurrence of the PKA catalytic subunit in photosynthetic organisms.

Amino Acid Sequence↗

PubMed1999

Identification of myosin II as a binding protein to the PH domain of protein kinase B.

Myosin II was identified as a binding protein to the pleckstrin homology (PH) domain of protein kinase B (PKB) in CHO cell extract by using the glutathione S-transferase-fusion protein as a probe. When myosin II purified from rabbit skeletal muscle was employed, myosin II was shown to bind almost exclusively to the PH domain of PKB among the PH domain fusion proteins examined. The purified myosin II bound to the PH domain of PKB with a Kd value of 1.1 x 10(-7) M. Studies with a series of truncated molecules indicated that the whole structure of the PH domain is required for the binding of myosin II, and the binding to the PH domain was inhibited by phosphatidylinositol 4,5-bisphosphate. These results suggest that myosin II is a specific binding protein to the PH domain of particular proteins including PKB.

Animals↗

PubMed1999

Effects of transiently expressed atypical (zeta, lambda), conventional (alpha, beta) and novel (delta, epsilon) protein kinase C isoforms on insulin-stimulated translocation of epitope-tagged GLUT4 glucose transporters in rat adipocytes: specific interchangeable effects of protein kinases C-zeta and C-lambda.

Atypical protein kinase (PK)C isoforms, zeta and lambda, have been reported to be activated by insulin via phosphoinositide 3-kinase, and have been suggested to be required for insulin-stimulated glucose transport. Here, we have examined the effects of transiently expressed wild-type (WT), constitutively active (Constit) and kinase-inactive (KI) forms of atypical PKCs, zeta and lambda, on haemagglutinin antigen (HAA)-tagged glucose transporter 4 (GLUT4) translocation in rat adipocytes, and compared these effects with each other and with those of comparable forms of conventional (alpha, beta) and novel (delta, epsilon) PKCs, which have also been proposed to be required for insulin-stimulated glucose transport. KI-PKC-zeta evoked consistent, sizeable (overall mean of 65%) inhibitory effects on insulin-stimulated, but not basal or guanosine-5'-[gamma-thio]triphosphate-stimulated, HAA-GLUT4 translocation; moreover, inhibitory effects of KI-PKC-zeta were largely reversed by co-transfection of WT-PKC-zeta. Like KI-PKC-zeta, KI-PKC-lambda inhibited insulin-stimulated HAA-GLUT4 translocation by approx. 40-60%, and the combination of KI-PKC-zeta and KI-PKC-lambda caused nearly complete (85%) inhibition. Of particular interest is the fact that inhibitory effects of KI forms of PKC-zeta and PKC-lambda were largely reversed by the opposite WT forms, i.e. PKC-lambda and PKC-zeta respectively. In contrast with KI forms of atypical PKCs, KI forms of PKC-alpha, PKC-beta2, PKC-delta and PKC-epsilon had little or no effect on insulin-stimulated HAA-GLUT4 translocation. Concerning the question of sufficiency, overexpression of WT-PKC-zeta enhanced insulin effects on HAA-GLUT4 translocation, whereas WT forms of PKC-alpha, PKC-beta2, PKC-delta and PKC-epsilon did not affect GLUT4 translocation; furthermore, Constit PKC-zeta evoked increases in HAA-GLUT4 translocation approaching those of insulin, but Constit forms of PKC-alpha and PKC-beta2 were without effect. Our findings suggest that, among PKCs, the atypical PKCs, zeta and lambda, appear to be specifically, but interchangeably, required for insulin effects on HAA-GLUT4 translocation.

Adipose Tissue↗

PubMed1999

Purification, characterization, and sequence determination of phospholipase D secreted by Streptoverticillium cinnamoneum.

Phospholipase D (PLD), secreted into the culture medium of an actinomycete, Streptoverticillium cinnamoneum, has been purified to homogeneity and characterized. The Stv. cinnamoneum PLD efficiently catalyzes both the hydrolysis and transphosphatidylation of various phospholipids, including phosphatidylethanolamine (PE), phosphatidylcholine (PC), and phosphatidylserine (PS). However, the substrate specificity differs between the two reactions; PE serves as the most preferred substrate for the hydrolysis, but PC and PS are better substrates than PE for the transphosphatidylation. In addition, the transphosphatidylation but not the hydrolysis of PE and PC is markedly activated on the addition of metal ions, especially Al3+. Nucleotide and amino acid sequence determination of the Stv. cinnamoneum PLD revealed the presence of common structural motifs identified in all PLD sequences from various species.

Aluminum↗