PART I. DESIGN AND SYNTHESIS OF DIHYDROOROTATE DEHYDROGENASE INHIBITORS WITH POTENTIAL ANTINEOPLASTIC ACTIVITY. PART II. DESIGN AND SYNTHESIS OF PROTEIN N-MYRISTOYLATION INHIBITORS AS POTENTIAL ANTINEOPLASTIC AGENTS

SHAWN A DEFREES, Purdue University

Abstract

Part I. The activity of dihydroorotate dehydrogenase (DHO-dehase) has been reported to decrease in hepatocellular carcinomas both in vitro and in vivo. DHO-dehase is a mitochondrial enzyme which is both a potential bottleneck along the accelerated de novo pyrimidine biosynthetic pathway and a potential therapeutic target for tumor inhibitors. A series of pyrimidine analogs of dihydroorotate and orotic acid was therefore designed and synthesized as potential inhibitors of DHO-dehase. The enzyme testing results established that the intact amide and imide groups of the pyrimidine ring and 6-position negative charge were necessary for enzyme inhibition. The testing results further suggest that a negatively charged enzyme substituent may be present near the 5-position of the pyrimidine ring and an enzyme-substrate metal coordination site may be near the N-1 and carboxylic acid positions of the pyrimidine ring. Analysis of the stereospecificity of the enzyme reaction by MS-MS indicates that the enzyme proceeds via a 5-pro S proton abstraction. The combined testing results were then used to define both conformational and steric substrate enzyme binding requirements and to propose a model for the binding of substrate and product to the DHO-dehase active site. Part II. Tyrosine protein kinases are a class of proteins derived from oncogenes responsible for cellular transformation. Several of these proteins require N-terminal myristoylation to direct the protein to its proper cellular location and for cellular transformation. Therefore, a series of inhibitors potentially capable of inhibiting myristic acid activation as well as the N-myristoylation step was designed and synthesized as potential antineoplastic agents. The best inhibitor of fatty acid activation and protein N-myristoylation of p561stra was 2-fluoromyristic acid suggesting that the myristoylation process utilizes a coenzyme A activated fatty acid. This compound also causes both ASK and rat XC cells to assume a fusiform morphology and after drug removal, the cells become multinucleated. Both myristoyl-N-glycine and myristoyl-N-glycine-(L)-serine inhibit db-cAMP induced tubulin reorganization in ASK cells. The most cytotoxic compound tested against 9PS cells in vitro was 1-chloro-2-dioxopentadecane which had an ED$\sb{50}$ value of 0.5 ug/ml.

Degree

Ph.D.

Subject Area

Organic chemistry

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