Constitutive and adaptive enzymes in mammalian cells

Fottrell, Patrick F (1962) Constitutive and adaptive enzymes in mammalian cells. PhD thesis, University of Glasgow.

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Functionally similar proteins from different species were examined by starch gel electrophoresis to determine the extent and nature of the molecular variation between homologous proteins from various sources. Marked variations were encountered when esterases, phosphatases, catalases and peroxidases from different species were compared. The electrophoresis patterns were so distinct that the species of origin could be recognized from the type of pattern produced. Organ specific esterase patterns were also demonstrated in several animals including mouse, rat, guinea pig and hen. In contrast osterase zymograms from different human organs were remarkably similar to each other. Species characteristic osterase patterns persisted in cultured cell lines which in some cases had been growing for many years in heterologous media. The osterase patters were not altered by the presence of organic esters in the growth medium. Therefore these patterns almost certainly reflect genetic differences. To explain how molecular heterogeneity is compatible with similarity in function, it was suggested that species variations were confined to those areas of protein molecules which were not essential for function. Several possibilities were considered to explain the occurrence of the large number of proteins displaying osterase activity, e.g. at least 16 in mouse liver. Investigations into the existence and mechanism of adaptive enzyme formation in animal cells were also undertaken. Animal cells maintained in culture were employed for this study because they provided a viable system, free from hormonal and nervous influence. Attempts were made to alter the levels of several enzymes in cultured cells by including substrates, products or related compounds in the growth medium. Under these conditions the levels of several enzymes including osterases, phosphatases, lactic dehydrogenase, glucose-6-phosphate dehydrogenase etc. were stable. On the other hand several examples of adaptive enzyme systems which provide more conclusive evidence for the existence of the phenomenon in animal cells were encountered. Glutamyl transferase activity in strains L and HLM was found to increase several fold when glutamine was removed from the culture medium. Active protein and RNA synthesis was necessary for induction of glutamyl transferase. Addition of glutamine to the medium of 'induced' cells resulted in a rapid disappearance of glutamyl transferase activity. In cell free extracts glutamyl transferase activity disappeared during incubation at 37

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: John Paul
Keywords: Molecular biology
Date of Award: 1962
Depositing User: Enlighten Team
Unique ID: glathesis:1962-73342
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56

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