Hypocholesterolemic effect of amaranth seeds was studied in male wistar strain albino rats as against Bengal gram. The results showed that liver weights were significantly higher in animals with hypercholesterolemia inducing diet. Contrarily, weights of other organs like brain, kidney, testes and spleen showed higher weights with amaranth and bengal gram diets. Serum lipid and TG (triglyceride) contents were lower and HDL-cholesterol fraction was higher and comparable with amaranth seed diet. Feeding with amaranth seed showed a definite hypocholesterolemic effect.

Glycine decarboxylse has bee sic solubUized from pea (Piwm sadvun) leaf ntochd as an oe wder. he enzyme was dependent on added ditldotdreltol and pyridoxal phpte for maxima activit. The enzyme preparation could catbyze the exchagte of CO2 Ito the carboxyl carbon of glycine, the reverse of the glycine decarboxylase reati by converting serine, NH1,, and CO into glycine, and 14C02release from 11-_4CIglyclne. The half-maximal concentrations for the glycIne-bcarbonate exchage reaction were 1.7 mIma glyclne, 16 mfllmolar NaH'4C0S, and 0.006 ill r pyrdxal p hte The enzyme (glycIne-bicarbonate ex e re on) was actve In the assay s for 1 hour and could be stored for over 1 mondth The ezymc h m appeare simar to that reported for the enzyme from a_hnals and bacteria but some antitatie dieces were noted. These included the tenacity of bIdn to the m n ra-m e, the concentration of pridoxal phosphate need for maxmu actvity, the r for dthothreItol for m m activity, and the total amnt of activity present. Now that this enzyme has been so-Ib led, a more detaied understanding of this important step In photorespiration sbould be possible.In those plants where the primary carboxylation reaction is catalyzed by the enzyme ribulose bisphosphate carboxylase, large amounts of the newly formed carbohydrate are oxidized back to CO2 by the process of photorespiration. The photorespiratory pathway, often called the photosynthetic carbon oxidation cycle, involves the synthesis and metabolism of glycolate. Glycolate is formed within the chloroplast and transported to the peroxisomes where it is oxidized to glyoxylate. The glyoxylate can be further oxidized (possibly by reaction with H202) to form formate and CO2 (3,4). The majority of the glyoxylate, however, is transaminated to glycine as long as sufficient glutamate and serine are available for the reaction (15, 18).The glycine formed within the peroxisomes is transported to the mitochondria. Recent data from this laboratory indicate that a transporter located in the inner membrane of the mitochondria is responsible for this movement (21). Once within the matrix of the mitochondria, the glycine is oxidized to C02, NHI+, and a C1 fragment that forms methylene THF.2 This reaction is catalyzed '

Glycemic index of grain amaranth, wheat and rice preparations was studied in non-insulin dependent diabetic subjects. Diets containing 50 g carbohydrate equivalent were given and post-prandial blood glucose estimated at different intervals. Glycemic index calculated for different experimental diets showed that GI of amaranth-wheat composite flour diet (25:75) was the least (65.6%) followed by wheat diet (65.7%), rice diet (69.2%), amaranth-wheat flour 50:50 (75.5%), and popped amaranth in milk (97.3%). Therefore 25:75 combination of amaranth and wheat, wheat and rice can be considered low GI food, 50:50 grain amaranth and wheat medium GI food and popped amaranth and milk combination high GI food.

ABSTRACICarboxymethoxylamine (amino-oxyacetate), methoxylamine, and acethydrazide are shown to be effective, although not completely specific, inhibitors of glycine oxidation by the isolated glycine decarboxylase multienzyme complex, mitochondria, protoplasts, and leaf discs from peas. The inhibition probably results from a reaction between these compounds and the pyridoxal 5-phosphate cofactor of the enzyme.The glycine decarboxylase multienzyme complex is a mitochondrial enzyme that is responsible for the photorespiratory oxidation of glycine. The enzyme complex is composed of at least four subunits: The P protein3 (PLP binding); the H protein (lipoamide containing); the T protein (THF binding); and the L protein (dihydrolipoamide dehydrogenase) according to the nomenclature of Kikuchi (5). The enzyme complex has been solubilized from pea leaf mitochondria in an active form (1 1) and purified to near homogeneity (12). The complex catalyzes the release of "'CO2 from [1-"'C]glycine dependent on the addition of PLP, THF, and NAD. It also catalyzes the exchange of "'CO2 with the carboxyl carbon of glycine and the synthesis of glycine from methylene THF, NADH, CO2, and NH4,. The isolated enzyme complex has a mol wt of about 290,000 and shows a strong dependence on the addition of DTT for full activity.Because of the unique role of this enzyme in photorespiration, substantial effort has been directed towards the identification of inhibitors of this enzyme. To date, three classes of inhibitors have been found: (a) compounds that react with PLP bound to the P protein, e.g. INH and cyanide; (b) compounds that react with the lipoamide cofactor of the H protein, like arsenite (1 1); and (c) structural analogs of glycine, such as aminoacetonitrile (16) and glycine hydroxamate (6). INH was the first reported inhibitor of glycine decarboxylase (10). It inhibits glycine oxidation by reacting with the PLP cofactor of the enzyme and is reasonably specific in that it shows little inhibition of photosynthesis under nonphotorespiratory conditions (13). INH, however, has limited usefulness because of the high concentrations (13) or '

No abstract

Mitochondria isolated from pea leaves (Pisum sativum L.) readily oxidized malate and glycine as substrates. The addition of glycine to mitochondria oxidizing malate in state 3 diminished the rate ofmalate oxidation.When glycine was added to mitochondria oxidizing malate in state 4, however, the rate of malate oxidation was either unaffected or stimulated. tricarboxylic acid cycle function.Several authors have suggested the total or partial inhibition of the tricarboxylic acid cycle in the light (1,2,7,10). Others have shown that the cycle continued in the light (3,8,15). The NADH produced by glycine oxidation can be used by malate dehydrogenase to reduce oxaloacetate to malate (17) and this malate can be linked by a shuttle system to the peroxisomal reduction of hydroxypyruvate to glycerate (12, 28).Isolated pea leaf mitochondria readily use both glycine and malate as substrates. In the experiments described, we added glycine to mitochondria metabolizing malate as a model reaction for determining the effect of photorespiratory glycine oxidation on tricarboxylic acid cycle function by these plants. MATERIALS AND METHODSDuring photosynthetic CO2 fixation by C-3 plants, a substantial amount of newly formed carbohydrate is oxidized back to CO2 by the process of photorespiration (29). The photorespiratory CO2 can arise either from the direct decarboxylation of glyoxylate (9, 19) or during the mitochondrial oxidation of glycine to NH3, C02, and methylene tetrahydrofolate by the enzyme glycine decarboxylase. In the latter case, NAD+ is the electron acceptor and it in turn is reoxidized by the mitochondrial electron transport chain (5, 17). Current data suggest that in soybean (20, 21) Mitochondria were isolated from 2-to 4-week-old greenhousegrown pea (Pisum sativum L.) seedlings. Younger plants could not be used because the high lipoxygenase activity precluded the isolation of well coupled mitochondria. After chilling for 1 h, the leaves and stems (approximately 300 g) were ground for 2 s in a 4-L Waring blender in 1 L of grinding medium (0.5 M sorbitol, 50 mM MOPS2-NaOH, pH 7.5, 5.0 mm EDTA, and 0.5% BSA). The inclusion of reducing agents, including 5 mm ascorbate, 2 mM DTT, 2 mm thioglycolate, or 10 mim cysteine, resulted in inconsistent coupling ratios and varying amounts of KCN-insensitive respiration and was avoided. The homogenate was filtered through two layers of Miracloth (Calbiochem) and the fitrate was centrifuged at 5,000g for 2 min.The mitochondria were then collected at 20,000g for 5 min. This pellet was resuspended in cold medium containing 0.5 M sorbitol, 20 mm MOPS-NaOH (pH 7.2), 0.1% BSA, and 2 mM glycine and centrifuged at l,000g for 10 min and then 7,000g for 10 min. The final pellet was resuspended in the same medium and either used directly or further purified on a Percoll (Pharmacia Fine Chemicals) gradient. In the latter case, 1 ml mitochondrial preparation was carefully layered atop a step gradient composed of (bottom to top) 2 ml each 40%1o, 25%, and 15% Percoll in 0.5 M sorbitol,...

No abstract

No abstract