The intermediary role of a steroid 8,14-dien-3β-ol system in ergosterol biosynthesis

1. A mechanism for the removal of the 14alpha-methyl group in ergosterol biosynthesis that involves the intermediacy of an 8,14-diene system is outlined. 2. In accordance with the requirements of this scheme, it is shown that 5alpha-ergosta-8,14-dien-3beta-ol is converted into ergosterol by Saccharomyces cerevisiae.     

The mechanism of the bond forming events in pyridine nucleotide linked oxidoreductases. Studies with epoxide inhibitors of lactic dehydrogenase and beta-hydroxybutyrate dehydrogenase.

2,3-Epoxybutyrate and 2,3-epoxypropionate act as effective competitive inhibitors of pig heart lactic dehydrogenase. KIapp for both inhibitors was pH dependent and varied according to the general equation KIapp = KI(1 +Ka/H+) which may be predicted if the binding of the epoxide to the E-NADH complex involves a compulsory protonation step. Values of KI(epoxybutyrate), KI(epoxypropionate) and pKa were estimated as 150 muM, 860 muM, and 6.8, respectively. The formation of an E-NADH epoxide inhibitor complex was followed directly by fluorescence measurements. Both epoxybutyrate and epoxypropionate enhanced fluorescence of the E-NADH complex and caused a 20-nm blue shift in the maximum emission wavelenght. The dissociation constants measured by fluorescence titration for both epoxides increased as the pH was raised reflecting a decreased affinity for the E-NADH complex. 2,3-Epoxybutyrate was also shown to inhibit beta-hydroxybutyrate dehydrogenase by a mechanism which is consistent with compulsory protonation prior to addition of the epoxide. These results are discussed in terms of a general mechanism for the bond forming events in pyridine nucleotide linked oxidore-ductases.     

Food and feeding preferences of Himalayan gray goral (Naemorhedus goral bedfordi) in Pakistan and Azad Jammu and Kashmir

Himalayan gray goral is endemic to Himalayas and Hindukush ranges. Analysis of 15 fecal samples and field observations from different areas of Pakistan and Azad Kashmir suggest that goral consumes foliage of a minimum of 28 plant species. Trees, shrubs and grasses appear in the ratio of 1:36:63 and hence the species is a grazer, though may opt for browsing when forced. The species mainly subsists on six species of grasses (Chrysopogon aucheri=17.97%, Themeda anathera=13.03%, Poa pratensis=11.23%, Digitaria decumbens=9.30%, Apluda mutica=7.51%, Aristida cyanatha=3.15%), though leaves of shrubs (Myrsine africana=11.38%, Daphne oleoides=8.87%, Carissa opaca=5.94%, Dodonaea viscose=4.79%, Rubus ellipticus=2.93%, Gymnosporia royleana=1.29%) are also consumed. Food preference indices (consumed/availability) suggest that grasses are highly preferred (16.86 times of availability), followed by shrubs (3.3 times of availability), whereas trees and herbs are not preferred. Food plants contain water (77.9±0.56%), ash (8.6±0.38%), sugars (6.8±0.16%), proteins (5.6%±0.28%) and fats (1.3±0.08%). Food provides 4,440 kcal of energy and 5.45 L of water/day/adult goral, which is sufficient to meet the requirements of the species. Grasses need to be ensured in the protected area separated for management of goral population. Zoo Biol 27:371–380, 2008. © 2008 Wiley‐Liss, Inc.