Identification of a dimeric KDG aldolase from Agrobacterium tumefaciens.

Agrobacterium tumefaciens is a Gram-negative bacterium and causative agent of Crown Gall disease that infects a variety of economically important plants. The annotated A. tumefaciens genome contains 10 putative dapA genes, which code for dihydrodipicolinate synthase (DHDPS). However, we have recently demonstrated that only one of these genes (dapA7) encodes a functional DHDPS. The function of the other nine putative dapA genes is yet to be determined. Here, we demonstrate using bioinformatics that the product of the dapA5 gene (DapA5) possesses all the catalytic residues canonical to 2-keto-3-deoxygluconate (KDG) aldolase, which is a class I aldolase involved in glucose metabolism. We therefore expressed, purified, and characterized recombinant DapA5 using mass spectrometry, circular dichroism spectroscopy, analytical ultracentrifugation, and enzyme kinetics. The results show that DapA5 (1) adopts an α/ß structure consistent with the TIM-barrel fold of KDG aldolases, (2) possesses KDG aldolase enzyme activity, and (3) exists as a tight dimer in solution. This study shows for the first time that dapA5 from A. tumefaciens encodes a functional dimeric KDG aldolase.

Urinary metabolic biomarkers of hepatocellular carcinoma in an Egyptian population: a validation study.

The advent of metabonomics has seen a proliferation of biofluid profiling studies of patients with hepatocellular carcinoma. The majority of these studies have been conducted in single indigenous populations making the widespread applicability of candidate metabolite biomarkers difficult. Presented here is a urinary proton nuclear magnetic resonance spectroscopy study of mainly hepatitis C virus infected Egyptian patients with hepatocellular carcinoma, which corroborates findings of a previous study from our group of mainly hepatitis B-infected Nigerian patients with hepatocellular carcinoma. Using multivariate statistical analysis, in the form of orthogonal signal-corrected partial least squared discriminant analysis, the sensitivity and specificity of the technique for distinguishing patients with tumors from healthy controls and patients with cirrhosis was 100%/94% and 81%/71%, respectively. Discriminatory metabolites included glycine, trimethylamine-N-oxide, hippurate, citrate, creatinine, creatine, and carnitine. This metabolic profile bears similarity to profiles identified in the Nigerian cohort of subjects indicative of tumor effects on physiology, energy production, and aberrant chromosomal methylation. This is the first study to identify similarly altered urine metabolic profiles of hepatocellular carcinoma in two etiologically and ethnically distinct populations, suggesting that altered metabolism as a result of tumorogenesis is independent of these two factors.

Hepatocellular carcinoma: diagnostics and screening.

Hepatocellular carcinoma (HCC) is the commonest primary hepatic malignancy and the third most common cause of cancer-related death worldwide. Incidence remains highest in the developing world and is steadily increasing across the developed world. The majority of HCC occurs on a background of cirrhosis, principally caused by two major risk factors, chronic hepatitis B and hepatitis C infection. Current diagnostic modalities, of ultrasound and α-fetoprotein, are expensive and lack sensitivity in tumour detection. Early diagnosis is integral to improved survival rates and there have been recent advances in technology that have enabled early identification of the process of hepatocarcinogenesis. This review outlines the epidemiological trends and risk factors for HCC; diagnostic techniques and current guidelines for screening and surveillance; and newer methods of screening.