An amino acid transport deficient strain of Neurospora crassa grown under nitrogen limitation in the presence of an amino acid produces extracellular L-amino acid oxidases. The enzymes were purified by a protocol consisting of affinity chromatography followed by molecular sieve chromatography which results in the purification to electrophoretic homogeneity of three L-amino acid oxidases. / The native molecular weight of each of the three enzymes is approximately 83,000 daltons and the subunit molecular weight is estimated to the 85,000 daltons for L-amino acid oxidase(,1) and 81,000 daltons for L-amino acid oxidase(,2) and L-amino acid oxidase(,3). / The three L-amino acid oxidases exhibit the same pH optimum, similar heat inactivation curves, similar substrate specificities and possess a flavin prosthetic group. / Tryptic digestion of each L-amino acid oxidase followed by reverse phase high performance liquid chromatography of the resulting peptides differentiates the enzymes from each other. Each enzyme displays a unique tryptic fingerprint and appears to be a distinct L-amino acid oxidase. / In addition, L-amino acid oxidases produced in response to a number of other stress conditions were isolated and compared to the oxidases induced by nitrogen limitation. The conditions included (1) reduced biotin concentration, (2) the presence of the amino acid analogue, para-fluorophenylalanine, or (3) reduced nitrogen plus D-methionine in the growth medium. Under each of these conditions, three oxidases are produced which display isolation characteristics identical to those of the three oxidases induced by nitrogen limitation. / A comparison of tryptic digestion fingerprints of the various L-amino acid oxidases led to the formation of three distinct classes. The tryptic fingerprints of members of Class 3 display almost complete homogeneity. It is likely that these enzymes are the same polypeptide. / Limited heterogeneity in the tryptic fingerprints among the members of Class 2 prevents such a definitive statement regarding their relationship to each other, but in light of the limited number of differences, it can be stated that the homology among the enzymes is extensive. The same conclusion can be reached regarding the four enzymes in Class 1. / Source: Dissertation Abstracts International, Volume: 45-08, Section: B, page: 2436. / Thesis (Ph.D.)--The Florida State University, 1984.
|OGILVIE, SUSAN., Florida State University
|Florida State University
|On campus use only.
|Dissertation Abstracts International
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