Spondyloepiphyseal dysplasia, chondroitin sulfate type: a possible defect of PAPS--chondroitin sulfate sulfotransferase in humans

Four patients with an unusual form of spondyloepiphyseal dysplasia excreted in the urine undersulfated chondroitin 6-sulfate (Biochem. Med. $\text{7}$, 415–423, 1973). The sera of these patients show a low activity of PAPS — chondroitin sulfate sulfotransferase, while the undersulfated chondroitin sulfate present in their urine is a much better acceptor of ${}^{35}\text{SO}{}_4$ than standard chondroitin sulfate when they are incubated with [${}^{35}\text{S}$]PAPS and normal sulfotransferases. These results suggest that in these patients the skeletal lesions are secondary to a defect in the synthesis of chondroitin sulfate involving specifically the sulfotransferase activity.     

Mutant cell lines resistant to azetidine carboxylic acid: Quantitative and qualitative differences in pyrroline-5-carboxylate synthase activity

Mutant Chinese hamster lung fibroblasts were selected that are resistant to the proline analog L-azetidine-2-carboxylic acid. Resistance in the two mutant cell lines is associated with two distinct alterations in pyrroline-5-carboxylate synthase, the enzyme that catalyzes the proline biosynthetic step leading from glutamic acid to pyrroline-5-carboxylate. In one mutant cell line, pyrroline-5-carboxylate synthase specific activity is increased 30-fold over the level in control cells. In the other mutant line, pyrroline-5-carboxylate synthase activity is not increased, but the enzyme has become insensitive to inhibition by ornithine and proline.     

Studies on the lipid metabolism of the metacercariae of Clinostomum complanatum (Trematoda: Digenea)

Metacercariae of Clinostomum complanatum possess considerable amounts of lipids. Fractionation of the lipids shows triglycerides and phospholipids as the major components whereas cholesterol and free fatty acids are minor components. Furthermore phospholipid fractions by thin layer chromatography reveal lecithin and cephalin as the major polar lipids whereas lysolecithin and lysocephalin are present in small fractions. The specific activity of lipase (E.C. 3.1.1.3) is 150.8 μg free fatty acids liberated/mg protein/h. Epinephrine, testosterone, insulin, sodium fluoride and iodoacetate stimulated, but 2-propanol inhibited, the lipase activity.     

Cyclic photophosphorylation reactions catalyzed by ferredoxin,methyl viologen and anthraquinone sulfonate. Use of photochemical reactions to optimize redox poising

The flavin analogue 5-deazariboflavin is a convenient catalyst for the photoreduction of low-potential redox compounds. In an anaerobic medium with Tricine buffer as the electron donor, 5-deazariboflavin is capable of photoreducing both ferredoxin and methyl viologen. We have used this method to conduct a comparative study of the Photosystem I photophosphorylation activities supported by the reduced forms of ferredoxin, methyl viologen and anthraquinone sulfonate. All of these catalysts are capable of generating high rates (200–500 μmol ATP/h per mg chlorophyll) of cyclic photophosphorylation, but only the activity dependent on ferredoxin exhibits sensitivity to antimycin A. This finding suggests that the size of the catalyst and its ability to approach the thylakoid membrane, rather than low-redox potential, governs antimycin A sensitivity. Ferredoxin-catalyzed activity is, however, less sensitive to inhibition by dibromothymoquinone than are the activities supported by methyl viologen and anthraquinone sulfonate. This discrepancy is due to binding of the inhibitor by ferredoxin.