Methylmalonic aciduria (MMA) is an autosomal recessive metabolic disorder with an incidence of 1 in 48,000, which may be due to a defect in the mitochondrial homodimeric enzyme methylmalonyl CoA mutase (mut MMA). mut MMA is subdivided into $mut sp circ$ and $mut sp-$ subclasses on the basis of complementation analysis; $mut sp circ$ cell lines have very low incorporation of ($ sp{14}$C) from propionate into acid precipitable material while incorporation in $mut sp-$ cells is increased when cells are incubated in cobalamin. Intragenic complementation was first observed with WG 1130, a $mut sp circ$ fibroblast line with a homozygous R93H mutation, that is capable of complementing MCM activity when fused with some $mut sp circ$ and some $mut sp-$ cells (1). Extensive intragenic complementation in mut MMA was subsequently observed. Fibroblasts cultured from thirteen unrelated patients (6 $mut sp-$, 7 $mut sp circ$) were fused in all possible pairwise combination and MCM activity was assayed in the heterokaryons by measuring the incorporation of ($ sp{14}$C) from propionate into acid precipitable material. Intragenic complementation, indicated by stimulation of ($ sp{14}$C) -propionate incorporation following cell fusion with polyethylene glycol, was observed in fusions involving twelve of the thirteen strains. Of these thirteen strains, mutations have been identified in six; four have a homozygous mutation (WG 1130 (R93H), WG 1511 (H678R), WG 1610 (G717V), WG 1609 (G630E)), and two cell lines are compound heterozygous (WG 1681 (G623R and G703R), WG 1607 (W105R and A377E)); the remainders are yet to be determined. These intragenic complementations will provide information for grouping the mutations in defined domains in order to correlate structure and function of MCM.

Methylmalonic aciduria is an autosomal recessive metabolic disorder, which may be due to a defect in the methylmalonyl CoA mutase (MCM) apoenzyme. The mut$ sp circ$ mutation is characterized by undetectable enzyme activity in cell extracts, and by the low incorporation of ($ sp{14}$C) propionate in the presence of hydroxocobalamin in culture. A mut$ sp circ$ fibroblast cell line, WG 1681, from an African-American male infant was shown to complement another mut$ sp circ$ cell line, WG 1130. Subsequent cloning and sequencing of cDNA from WG 1681 identified two previously described homozygous polymorphisms: H532R and V671I(1). In addition, compound heterozygosity was observed for two novel changes at highly conserved sites: G623R and G703R. Hybridization of allele specific oligonucleotides to PCR amplified MCM exons from WG 1681 and family members identified a clinically normal mother, sister and half-brother as carriers of the G703R change in cis with both polymorphisms. The putative father was not identified as a carrier of the G623R change. transfection of each change, singly and in cis with both polymorphisms, into GM1673 cells demonstrated a lack of stimulation of ($ sp{14}$C) propionate uptake in the absence and presence of OH-Cbl, in comparison to controls. Co-transfection of each separate mutation with the previously identified R93H mutation of WG 1130 (2) stimulated propionate uptake. These results indicate that G623R and G703R are novel mutations responsible for deficient MCM activity and the mut$ sp circ$ phenotype in WG 1681, and both mutations are independently capable of complementing the R93H mutation of WG 1130.

This thesis describes three studies on mammalian 25-hydroxyvitamin D$ sb3$-24-hyroxylase (24-hydroxylase), the first enzyme in the C24-oxidation pathway, a major catabolic pathway for vitamin D metabolites in kidney and other target tissues for vitamin D hormone. The first study examines the involvement of protein kinase C in the regulation of 24-hydroxylase activity in mouse kidney. Evidence is presented supporting a stimulatory role for protein kinase C in the regulation of constitutive, but not inducible, renal 24-hydroxylase. The kinase is also implicated in the aberrant expression of renal vitamin D metabolism in the mutant X-linked hypophosphatemic (Hyp) mouse. The second study investigates the mechanism(s) by which forskolin, a classic activator of adenylate cyclase, inhibits 24-hydroxylase activity in mouse kidney. Both the traditional cAMP-dependent mechanism and a novel cAMP-independent mode of action are observed. A direct interaction between forskolin and the substrate binding site of 24-hydroxylase is suggested for the latter based on kinetic analyses and structural similarities between the diterpene and the steroid substrate for the hydroxylase. The third study addresses the structural relationship between renal 1-hydroxylase and renal and target cell 24-hydroxylase(s) by assessing 24-hydroxylase activity in patients with vitamin D dependency rickets type I (VDDR-I), a Mendelian disorder of 1-hydroxylase function. Both constitutive renal 24-hydroxylase, indirectly ascertained through measurement of circulating levels of relevant vitamin D metabolites, and inducible target cell 24-hydroxylase, directly measured in cultured skin fibroblasts, are shown to be intact in VDDR-I patients undergoing calcitriol therapy. These findings suggest that the 1- and 24-hydroxylase activities likely represent or contain distinct gene products.

Prolidase deficiency (MIM 26413), an autosomal recessive phenotype, is caused by rare alleles at a locus on chromosome 19cent.-q13.2. The clinical phenotype is pleiotropic (affecting skin, brain, etc.) and of variable expressivity (benign to early death). I established skin fibroblast cultures from 6 homozygous probands and 6 obligate heterozygotes, purified prolidase (E.C. 3.4.13.9, a homodimer) from normal human fibroblasts, raised a monospecific rabbit antiserum to the subunit, and studied its biosynthesis. Pulse-chase immunoprecipitation experiments showed that the subunit is synthesized in the cytosol as a 58 KDa. polypeptide and not processed further. Homozygous prolidase-deficient cell strains expressed 3 classes of mutant alleles which by complementation analysis mapped to one locus. The alleles were designated CRM$-$ (nul), CRM+ activity/size variant, and CRM+ activity variant. Heterozygotes carrying CRM$-$ alleles have heat stable prolidase (50$ sp circ$C, 1hr); heterozygotes carrying CRM+ variant alleles have heat labile enzyme. The finding implies that variant CRM+ allele(s) can confer negative allelic complementation on the dimeric enzyme (dominant relative phenotype). CRM$-$ homozygous cells contain varying amounts of an alternative imidodipeptidase-like activity. The variant prolidase allele (major gene) and amount of alternative "prolidase" activity (modifier gene) are apparently both determinants of the associated clinical phenotype in prolidase deficiency. I obtained and sequenced a tryptic peptide from human kidney prolidase for synthesis of oligonucleotide probes in the future.

Thesis (doctoral)--University of Wisconsin-Madison, 2000. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Prefatory material introducing a collection of articles spanning fifty years of research into inborn errors of metabolism. Table of Contents: 1. Introduction -- 2. Background information about inborn errors of metabolism -- 3. Lessons from phenylketonuria [PKU] -- 4. My role in developing new medical foods -- 5. My role in solving an epidemic of benzyl alcohol poisoning in premature infants -- 6. My role in galactosaemia research -- 7. My start in the metabolic world - screening tests in urine -- 8. My experiences in disaster relief -- 9. My first appearance in the medical literature -- 10. A selection of rare and unusual diseases -- 11. Tyrosinaemia type II; tyrosine aminotransferase deficiency -- 12. Iminodipeptiduria due to prolidase deficiency -- 13. Citrullinaemia -- 14. Rippling muscle disease -- 15. A fatal X-linked disorder of diarrhoea, diabetes mellitus and immune dysregulation -- 16. Infantile Refsum disease -- 17. Hereditary hypocalcuric hypercalcaemia -- 18. Carbohydrate deficient glycoprotein disease type IAPKU -- 19. Thiamine-responsive diabetes and deafness -- 20. Folinic acid-responsive seizures: a false alarm -- 21. S-adenosylmethionine hydrolase deficiency -- 22. Deficiency of complex III of the respiratory chain -- 23. Current research: quantitation of infant sucking behaviour -- 24. Discussion and summary.

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Thesis (M.P.H.)--University of Texas Health Science Center at Houston, School of Public Health, 2008. / Source: Masters Abstracts International, Volume: 46-05, page: 2641. Advisers: Jan Bressler; Raol Caetano. Includes bibliographical references.