Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.10.3.3 (ascorbate oxidase)
 778 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rat Schwann cells cultured with dorsal root ganglion neurons in a serum-free defined medium fail to ensheathe or myelinate axons or assemble basal laminae. Replacement of defined medium with medium that contains human placental serum (HPS) and chick embryo extract (EE) results in both basal lamina and myelin formation. In the present study, the individual effects of HPS and EE on basal lamina assembly and on myelin formation by Schwann cells cultured with neurons have been examined. Some batches of HPS were unable to promote myelin formation in the absence of EE, as assessed by quantitative evaluation of cultures stained with Sudan black; such HPS also failed to promote basal lamina assembly, as assessed by immunofluorescence using antibodies against laminin, type IV collagen, and heparan sulfate proteoglycan. The addition of EE or L-ascorbic acid with such HPS led to the formation of large quantities of myelin and to the assembly of basal laminae. Pretreatment of EE with ascorbic acid oxidase abolished the EE activity, whereas trypsin did not. Other batches of HPS were found to promote both basal lamina and myelin formation in the absence of either EE or ascorbic acid. Ascorbic acid oxidase treatment or dialysis of these batches of HPS abolished their ability to promote Schwann cell differentiation, whereas the subsequent addition of ascorbic acid restored that ability. Ascorbic acid in the absence of serum was relatively ineffective in promoting either basal lamina or myelin formation. Fetal bovine serum was as effective as HPS in allowing ascorbic acid (and several analogs but not other reducing agents) to manifest its ability to promote Schwann cell differentiation. We suggest that ascorbic acid promotes Schwann cell myelin formation by enabling the Schwann cell to assemble a basal lamina, which is required for complete differentiation.
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PMID:Differentiation of axon-related Schwann cells in vitro. I. Ascorbic acid regulates basal lamina assembly and myelin formation. 362 5

The cDNA library of the Japanese lacquer tree (Rhus vernicifera) was constructed by the reverse transcription of mRNA. A cDNA encoding laccase was amplified by PCR using primers based on the N-terminal amino acid sequences of the purified laccase and its peptide fragments formed by digestions with chymotrypsin and trypsin, and subcloned. The laccase cDNA clone contained a single, large open reading frame of 1599 nucleotides, encoding a protein of 533 amino acids with a calculated molecular mass of 58981 Da. The lacquer laccase was found to have 42 to 62% identity with other plant laccases and 20 to 24% identity with microorganism laccases at the deduced amino acid level. Differing from microorganism laccases the lacquer laccase utilizes a Met residue in addition to one Cys and two His residues to construct the type 1 Cu site. The secondary structure of the lacquer laccase was predicted to mainly consist of the beta-structure (28.7%) and loop and random structures (67.0%). The alpha-helix content was predicted to be only 4.3%. The location of these secondary structures was assumed to be very similar to those of ascorbate oxidase and fungal laccase, the crystal structures of which have been determined.
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PMID:Primary structure of a Japanese lacquer tree laccase as a prototype enzyme of multicopper oxidases. 1212 69