Darrell H. Mallonee

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The 1923 bp cDNA for rat hepatic cholesteryl ester hydrolase (CEH) was cloned by screening a lambda gt11 expression library with an oligonucleotide containing the consensus active site sequence for cholesteryl esterases. Expression of a fusion protein, cross-reacting with antibody to the purified liver CEH, was demonstrated by Western blot analysis. The(More)
The human intestinal Eubacterium sp. strain VPI 12708 has been shown to have a multistep biochemical pathway for bile acid 7alpha-dehydroxylation. A bile acid-inducible operon encoding 9 open reading frames has been cloned and sequenced from this organism. Several of the genes in this operon have been shown to catalyze specific reactions in the(More)
Two bile acid-inducible polypeptides from Eubacterium sp. strain VPI 12708 with molecular weights of 27,000 and approximately 45,000 have previously been shown to be encoded by genes residing on a 2.9-kb EcoRI fragment. We now report the cloning and sequencing of three additional overlapping DNA fragments upstream from this EcoRI fragment. Together, these(More)
Eubacterium sp. strain VPI 12708 has several bile acid-inducible (bai) genes which encode enzymes in the bile acid 7 alpha-dehydroxylation (7 alpha DeOH) pathway. Twelve 7 alpha DeOH-positive intestinal bacterial strains were assayed for 7 alpha DeOH activity, and 13 strains were tested for hybridization with bai genes. Cholic acid 7 alpha DeOH activity(More)
Bile acid synthesis occurs mainly via two pathways: the "classic" pathway, initiated by microsomal cholesterol 7alpha-hydroxylase (CYP7A1), and an "alternative" (acidic) pathway, initiated by sterol 27-hydroxylase (CYP27). CYP27 is located in the inner mitochondrial membrane, where cholesterol content is very low. We hypothesized that cholesterol transport(More)
Eubacterium sp. strain VPI 12708 expresses inducible bile acid 7alpha-dehydroxylation activity via a multistep pathway. The genes encoding several of the inducible proteins involved in the pathway have been previously mapped to a bile acid-inducible (bai) operon in Eubacterium sp. strain VPI 12708. We now report the cloning, sequencing, and characterization(More)
The initial and rate-limiting step in the classic pathway of bile acid biosynthesis is 7alpha-hydroxylation of cholesterol, a reaction catalyzed by cholesterol 7alpha-hydroxylase (CYP7A1). The effect of CYP7A1 overexpression on cholesterol homeostasis in human liver cells has not been examined. The specific aim of this study was to determine the effects of(More)
BACKGROUND & AIMS The rate of 12alpha-hydroxylation of bile acid intermediates is believed to determine the ratio of cholic acid (CA) to chenodeoxycholic acid (CDCA) biosynthesis and the overall hydrophobicity of the bile acid pool. The aim of this study was to determine the effects of the level of expression of sterol 12alpha-hydroxylase (CYP8b1) and(More)
In the liver, sterol 27-hydroxylase (CYP27) participates in the classic and alternative pathways of bile acid biosynthesis from cholesterol (Chol). In extrahepatic tissues, CYP27 converts intracellular Chol to 27-hydroxycholesterol (27OH-Chol), which may regulate the activity of 3-hydroxy-3-methylglutaryl CoA reductase (HMG-CoA-R). This study attempts to(More)
The baiB gene from Eubacterium sp. strain VPI 12708 was previously cloned, sequenced, and shown to be part of a large bile acid-inducible operon encoding polypeptides believed to be involved in bile acid 7 alpha-dehydroxylation. In the present study, the baiB gene was subcloned and expressed in Escherichia coli and shown to encode a bile acid-coenzyme A(More)