Comparative Study of Molecular Size and Structure of Exo- -Glucanases from Kluyveromyces and Other Yeast Genera: Evolutionary and Taxonomic Implications

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Abstract
A comparative study was made of the MW of the exo-.beta.-glucanases (EC 3.2.1.58) of species belonging to Kluyveromyces or to various other yeast genera. Their immunological distances were determined with the exo-.beta.-glucanases from K. fragilis, K. phaseolosporus, K. aestuarii, and Saccharomyces cerevisiae as references. The molecular sizes of the enzymes were estimated by polyacrylamide gel exclusion chromatography. Immunological comparison was done by the microcomplement fixation technique. The MW of the enzymes from ascomycetous species ranged from 24 .times. 103 to 63 .times. 103, but the majority of the species, including most species of Kluyveromyces, contained exo-.beta.-glucanases with MW from 35 .times. 103 to 45 .times. 103. Immunological identity was observed among the exo-.beta.-glucanases from K. fragilis (reference species), K. marxianus, K. bulgaricus, K. cicerisporus and K. wikenii. Closely related were K. phaseolosporus (reference species), K. delphensis, K. lactis, K. vanudenii and K. drosophilarum. Also closely related were S. cerevisiae (reference species), S. italicus, S. uvarum and S. chevalieri. The exo-.beta.-glucanase from K. aestuarii showed low degrees of homology with those from all tested species of Kluyveromyces. Ascospore shape apparently has little significance in the phylogeny of this genus. Other evolutionary implications are discussed.