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Hexokinase catalyzes the first step in cerebral glucose utilization and is a rate-limiting enzyme in glycolysis. Glucose utilization is tightly coupled to cerebral blood flow so that during ischemia the brain has a decreased supply of glucose, as well as oxygen. We studied hexokinase enzymatic activity in a newborn piglet model of ischemia-reperfusion to determine if any changes in the activity or mitochondrial binding of the enzyme occurred. We observed that mitochondrial binding of cortical HK increased from 55 to 71% with ischemia and returned toward control levels, but did not completely recover, after 2 h of reperfusion.

Hexokinase 1 (HK1) purified from rat brain exhibits protein kinase activity, including autophosphorylation and phosphorylation of other protein substrates. The amino acid specificity of rat brain autophosphorylation was analyzed with monoclonal antibodies directed against phosphotyrosine and by acid hydrolysis of the phosphorylated enzyme. The results show that serine, threonine, and tyrosine residues are phosphorylated after incubation with ATP. The stoichiometry of this phosphorylation was 0.2 mole phosphate per mole hexokinase after 30 min of incubation. Evaluation of freshly isolated HK1 with monoclonal anti-phosphotyrosine antibody indicates that the enzyme is phosphorylated at a basal level in its native state. We concluded that rat brain HK1 is a dual specificity protein kinase that is phosphorylated physiologically.

Newborn screening for the hemoglobinopathies has been shown to reduce morbidity and mortality, particularly for sickle cell anemia, by facilitating initiation of penicillin prophylaxis by 4 months of age. The purpose of the current investigation was to determine whether molecular genetic follow-up testing could be introduced into a neonatal hemoglobinopathy screening program and, if successfully introduced, whether it would reduce time to diagnostic confirmation. Between July 1, 1991, and October 7, 1992, 518 original dried blood specimens were referred from the Texas Department of Health Neonatal Hemoglobinopathy Screening Program for molecular genetic follow-up testing. Allele-specific cleavage (ASC) after amplification with matched and mismatched polymerase chain reaction primers was compared to allele-specific oligonucleotide (ASO) hybridization. By November 2, 1992, molecular genetic analyses were definitive in 506, and agreement was observed between ASC and ASO hybridization in all specimens analyzed. Approximately 13% of those initially screened FS were considered probable S/beta-thal by DNA and RNA testing. Rapid molecular genetic analysis contributed to a substantial reduction of the mean age at confirmation by approximately 50%, to about 2 months of age. ASC is a reliable method for molecular genetic analysis of dried blood specimens, providing methodology which can be readily automated. An automated method is demonstrated that is based on microtiter plate technology and will significantly reduce labor intensity and costs, while increasing sample throughput. Even with current manual testing methods, DNA and RNA analysis of initial newborn screening specimens will reduce the age at confirmation well under 4 months, the age cut-off for effective initiation of penicillin prophylaxis.

Protocols for human gene therapy have been approved and a number of investigative trials are in place. While somatic gene therapy is favored over germline therapy, it must be recognized that transformation of somatic cells may occur inadvertently. Ex vivo and in vivo approaches offer two different strategies for genetic intervention and are discussed in the context of therapy for inborn errors of metabolism, brain tumors and other neurological diseases, and AIDS and other infectious diseases. Current technology appears quite promising, but serious limitations remain before routine application of gene therapy is possible.

Hexokinase 1 (HK1) is one of four mammalian HK isoenzymes and maps to human chromosome 10. Two yeast artificial chromosomes (YACs) were identified in the Washington University human YAC library using polymerase chain reaction (PCR) primers designed with knowledge of the human HK1 cDNA sequence. YAC B129B12 is 120 kb in length and maps entirely to chromosome 10. YAC A159D5 is 400 kb in length and appears to have resulted from a recombination of chromosome 10 with non-chromosome 10 material. We report these YACs as potential resources for those interested in HK1 gene organization and mapping, as well as those desiring additional genomic information and markers on chromosome 10.

Direct genotypic analysis for the common Caucasian cystic fibrosis mutation (delta F508) was performed using dried blood specimens in a filter paper matrix (neonatal screening blotter). DNA was obtained from dried and liquid blood samples, amplified, and analyzed by polyacrylamide gel electrophoresis. Additionally, intact 4-mm-diameter punched discs from blotters containing dried blood specimen were used in the amplification reactions and analyzed by electrophoresis. The results agreed completely between these three sample types, demonstrating the feasibility of molecular genetic confirmation of the delta F508 mutation from the neonatal screening blotter among those with positive CF screening results. Such a program could reduce follow-up testing by at least 50% in a CF newborn screening program and would identify immediately those families who would benefit from carrier detection for the delta F508 allele.

Porin is the pore-forming protein involved in the movement of adenine nucleotides across the outer mitochondrial membrane (OMM). Hexokinase and glycerol kinase interact with porin on the outer surface of the OMM in a manner which provides these enzymes with preferred access to the ATP generated in the mitochondrion. We review recent evidence which permits refinement of our knowledge of these proteins and their interactions at the OMM. The involvement of this system in metabolic microcompartmentation is discussed, as well as possible pathological consequences of its disruption in malignancy and genetic deficiencies of hexokinase, glycerol kinase, and porin.

Conditions for blood storage are chosen to assure adequate levels of adenosine triphosphate (ATP) and 2,3-diphosphoglycerate (2,3-DPG). Because of the invasive nature of the techniques, biochemical assays are not routinely used to measure levels of these compounds in stored blood. However, 31P NMR spectroscopy measures phosphorylated intermediates in intact cells and could be used without disruption of the storage pack. We compared levels of ATP and 2,3-DPG measured by 31P spectroscopy and standard enzyme-linked biochemical assays in whole blood (WB) and packed red blood cells (PRBCs) at weekly intervals during a 35-day storage period. NMR demonstrated a marked decrease in 2,3-DPG and an increase in inorganic phosphate after the first week of storage. No significant differences in ATP concentrations were seen in WB during the storage period, but a significant decrease in ATP in PRBCs was documented. There was good agreement in levels of ATP and 2,3-DPG measured by NMR and biochemical techniques. 31P NMR spectroscopy is a noninvasive technique for measuring ATP and 2,3-DPG which has a potential use in quality assurance of stored blood.

The porins are a class of voltage-dependent, anion-selective, channel-forming proteins located in the outer mitochondrial membrane (OMM). The porins are responsible for passage of adenine nucleotides across the OMM, as well as for specific binding of hexokinase and glycerol kinase. This porin-kinase complex has direct access to ATP generated by mitochondrial oxidative phosphorylation and may be important in the regulation of glycolysis. Porin had not been described previously in humans but, due to its importance in bioenergetics, would be expected to be present, especially in organs requiring a large and constant supply of energy. We therefore postulated that porin would occur in human myocardium where it would be important in cardiac function. Polyclonal antibodies to bovine myocardial and rat liver porins were utilized in transblotting experiments after polyacrylamide gel electrophoresis of human heart preparations from atria, ventricles, papillary muscles, and interventricular septum. These immunoblots demonstrated selective staining of a 34-kDa band. This was identical to the results obtained with purified porin and the antibodies. Also notable was the finding that the vast majority of this staining was found in the homogenate pellet after high speed centrifugation (20,000g), as would be expected for a mitochondrial protein. The demonstration of human cardiac porin by immunoblotting with rat liver and bovine myocardial porin antibodies is the first demonstration of cross-species identification of the porins. The success of this approach undoubtedly occurred because of strong homology between porins from a variety of species.

A simple and reliable method is described which is suitable for estimation of a whole blood phenylalanine concentration for the patient with PKU in various settings including the physician's office and the home. Excellent correlations were obtained between this method and weighed phenylalanine standards, as well as with measurement of phenylalanine in serum, plasma, and whole blood, using the McCaman-Robins fluorometric assay. Increasing the frequency and rapidity of feedback to the patient should improve metabolic control, just as home glucose monitoring has for the patient with diabetes mellitus. This method is immediately adaptable to monitoring patients with tyrosinemia, and with substitution of the appropriate amino acid ammonia lyase could be used for other amino acidemias.

Hexokinase (EC 2.7.1.1) catalyzes the first step in glucose metabolism, using ATP for the phosphorylation of glucose to glucose 6-phosphate. A portion of the HK1 gene was cloned by mixed oligonucleotide primer amplification of cDNA using primers of high complexity. The amino acid sequence for a partial fragment of bovine cardiac muscle HK was determined and used to create primer mixtures of 256- and 1024-fold complexity. Two products were generated from bovine cardiac muscle cDNA which show 82% nucleotide and 93% amino acid identity with a region of rat brain HK1 and cDNA. This work demonstrates that extension and amplification of cDNA probes may be successful even when amino acid sequence data indicate substantial codon degeneracy.