Dissociation of hydroxylase and lyase activities by site-directed mutagenesis of the rat P45017 alpha.

Site-directed mutagenesis of the arginine-rich region within the putative active site of the rat testicular P45017 alpha (17 alpha-hydroxylase cytochrome P-450, the product of P450XVII gene) was performed to identify specific amino acids that contribute to either the hydroxylase or lyase activities catalyzed by this enzyme. The conversion of Arg346 to alanine differentially abolished lyase activity without affecting hydroxylase activity, resulting in an accumulation of the 17 alpha-hydroxylated intermediate, and partial lyase activity was recovered by conversion of this mutant to Lys346. Similar results were obtained with the conversion of Arg357 to alanine, although this mutant also diminished hydroxylase activity, and full lyase and hydroxylase activities were recovered with a lysine in this position. Major reductions in hydroxylase activity were apparent with the conversion of Arg363 to Ala, and this inhibition was reversed by a lysine at position 363. In contrast, differential effects were not observed with the mutants Arg361 Ala, Arg361 Lys, or Tyr334Phe. Both mutations at the Arg361 position resulted in a total loss of hydroxylase and lyase activities, and mutation at the Tyr334 position had no effect on either activity. The identification of specific amino acids that are essential for either the hydroxylase or lyase reaction indicates that the steroid substrate-protein interaction changes during the course of the two consecutive reactions and reveals the potential for separation of the two activities by chemical and biological modulators within the active site region of the P45017 alpha.     

Schizophrenia, eye movements, and biocultural heterogeneity

Smooth-pursuit eye-tracking dysfunction is a putative genetic trait marker for schizophrenia. In this study 88 Japanese schizophrenics from Kyushu and Okinawa were examined for the marker using precise high-resolution instrumentation: 76% of the schizophrenics from Kyushu and 89% of those from Okinawa had pursuit dysfunction. The presence of the culture-neutral smooth-pursuit marker for schizophrenia in Japan demonstrates that the etic concept "schizophrenia" is cross-culturally valid. Furthermore, the ubiquity of the marker in biologically and culturally diverse populations may indicate a limit on the extent of meaningful heterogeneity likely to be discovered within the condition.     

Effect of N-(3-phenyl-2-propenyl)-1-deoxynojirimycin on the lectin binding to HIV-1 glycoproteins

The effect of N-(3-phenyl-2-propenyl)-1-deoxynojirimycin (ppDNM) on the lectin binding to HIV-1 glycoprotein was analyzed by using biotinylated lectins of various sugar specificities as probes. ppDNM potentially inhibited HIV-1-induced syncytium formation and viral infectivity of HIV-1 without cytotoxicity. The lectin binding assay showed that ppDNM treatment reduced Con A binding to gp120 of HIV-1.     

Isolation of NPY-25 (neuropeptide Y[12-36]), a potent inhibitor of calmodulin, from porcine brain

In the present purification of low molecular weight fractions (Mr: 2000-4000) containing basic peptides, twenty nmol of novel calmodulin binding peptide, possessing a potent affinity for calmodulin, was isolated from 18 kg of porcine brain. By analysis with gas phase sequencer, the sequence was determined to be APAEDLARYYSALRHYINLITRQRY. Carboxy terminus of the peptide was determined to be Tyr-NH2. The peptide was a carboxy terminal pentacosanepeptide of neuropeptide Y and was termed NPY-25. NPY-25 competitively inhibited the activation of cAMP-phosphodiesterase through CaM binding in a Ca++ dependent fashion, but did not inhibit the basal activity of cAMP phosphodiesterase. NPY-25 elicited a more potent activity than did neuropeptide Y. IC50 values of NPY-25 and Neuropeptide Y were 0.06 microM and 0.54 microM respectively.     

Chondroitin sulfate proteoglycan in the extracellular matrix of the canine superior olivary nuclei

The perineuronal extracellular matrix of the canine superior olivary nuclei was examined by the histochemical method. The extracellular matrix was stained with Alcian blue (pH 1.0 and 2.5), high iron diamine and ruthenium red. The staining intensity of Alcian blue in the extracellular matrix was remarkably reduced after chondroitinase ABC digestion but not after that of heparitinase or hyaluronidase. These results indicate that the extracellular matrix consists of proteoglycans and contains the chondroitin sulfate proteoglycan.     

Histidine decarboxylase activities in mutant mice deficient in mast cells

The histamine contents were very low in the whole bodies of various types of mutant mice (W^v/W^v, W^v/W, W/W), in which the number of mast cells was decreased, but the L-histidine decarboxylase activities in these mutant mice were not much lower than in control wild type mice. These findings suggest the presence of high histidine decarboxylase activity in cells other than mast cells. Histidine decarboxylase in the whole body of mice was difficult to assay, because the enzyme was rapidly destroyed by proteases, but inclusion of a protease inhibitor, such as Leupeptin, Antipain, Chymostatin, or Pepstatin in the assay mixture permitted the accurate assay of histidine decarboxylase in crude extracts.     

Active oxygen participation in chlorophyll destruction and lipid peroxidation in SO2-fumigated leaves of spinach

Chlorophyll a and carotenoids of spinach began to be destroyed2 to 3 hr after fumigation with 2 ppm SO₂ under light, whereaschlorophyll b was undamaged during 8 hr of exposure to SO₂.Pheophytin a was not affected by the fumigation. When disks excised from leaves fumigated with SO₂ at 2 ppm for2 hr were illuminated, chlorophyll a and carotenoids were brokendown, while they were not destroyed in darkness. The destructionof these pigments was suppressed under nitrogen. Chlorophylla destruction was inhibited by l,2-dihydroxybenzene-3,5-disulfonate(tiron), hydro-quinone and ascorbate, but not by l,4-diazabicyclo-[2,2,2]-octane(DABCO), methio-nine, histidine, benzoate and formate. Chlorophylla destruction was inhibited by phenazine methosulfate but stimulatedby methyl viologen. Addition of superoxide dismutase (SOD) tothe homogenate of SO₂-fumigated leaves inhibited the chlorophylla destruction. The activity of endogenous SOD was reduced to40% by 2-hr fumigation before the loss of chlorophyll was observed.These results suggest that chlorophyll a destruction by SO₂was due to superoxide radicals (O₂^–). Moreover, malondialdehyde (MDA), a product of lipid peroxidation,was formed in SO₂-fumigated leaves. MDA formation was inhibitedby tiron, hydroquinone and DABCO but not by benzoate and formate.MDA formation was increased by D₂O. These results suggest thatlipid peroxidation in SO₂-fumigated leaves was due to singletoxygen ¹O₂ produced from O_2^–. (Received May 15, 1980; )