The Relation Between Growth, Conidiation and Trehalase Activity in Neurospora Crassa

In the thermophilic fungus Thermomyces lanuginosus, invertase displays an unusual pattern of development: the induced activity begins to diminish even before any substantial quantity of sucrose has been utilized or an appreciable amount of biomass has been produced. Despite this pattern of invertase activity, neither the growth rate nor the final mycelial yield is affected adversely. T. lanuginosus invertase is a thiol protein and the enzyme is active when specific sulfhydryl group(s) is in the reduced state. Measurements of reduced coenzyme and glutathione pools in sucrose-grown mycelia excluded oxidative stress as the primary reason for the observed decline in invertase activity. Rather, this unusual pattern of invertase is considered to be due to its localization in the hyphal tips. At the early stage of growth, the number of hyphal tips per unit mass of mycelium is maximum, whereas at later times their numbers do not increase in proportion to the biomass. As a result invertase activity shows an apparent inverse relationship with biomass. The enzyme activity disappears when the inducing carbon source is consumed and growth is completed. ß

Section: Discussionsupporting

confidence: 89%

An unusual pattern of invertase activity development in the thermophilic fungus Thermomyces lanuginosus

Chaudhuri

1999

“…This pattern was explained on the basis that a major portion of invertase is distributed in the intramural space [10] and the increase in enzyme activity reflects the amount of wall material in old mycelium. Similar pattern was also seen for the intracellular trehalases in N. crassa [11], and in T. lanuginosus (present study). (2) The (induced) invertase activity shows an inverse relationship with the amount of biomass and disappears upon the exhaustion of the carbon source (sucrose), as in T. lanuginosus (Fig.…”

Section: Discussionsupporting

confidence: 89%

An unusual pattern of invertase activity development in the thermophilic fungusThermomyces lanuginosus

Chaudhuri¹,

Bharadwaj²,

Maheshwari³

1999

In the thermophilic fungus Thermomyces lanuginosus, invertase displays an unusual pattern of development: the induced activity begins to diminish even before any substantial quantity of sucrose has been utilized or an appreciable amount of biomass has been produced. Despite this pattern of invertase activity, neither the growth rate nor the final mycelial yield is affected adversely. T. lanuginosus invertase is a thiol protein and the enzyme is active when specific sulfhydryl group(s) is in the reduced state. Measurements of reduced coenzyme and glutathione pools in sucrose-growth mycelia excluded oxidative stress as the primary reason for the observed decline in invertase activity. Rather, this unusual pattern of invertase is considered to be due to its localization in the hyphal tips. At the early stage of growth, the number of hyphal tips per unit mass of mycelium is maximum, whereas at later times their numbers do not increase in proportion to the biomass. As a result invertase activity shows an apparent inverse relationship with biomass. The enzyme activity disappears when the inducing carbon source is consumed and growth is completed.

“…The behavior of trehalase in T. lanuginosus was similar to that in N. crassa [12,13]. In T. lanuginosus the maximal speci¢c activity of trehalase (2 U (mg protein) 31 ) occurred 84^96 h of growth.…”

Section: Inter-relationship Between Carbon Source Utilization Growthsupporting

confidence: 55%

A comparison of thermal characteristics and kinetic parameters of trehalases from a thermophilic and a mesophilic fungus

Bharadwaj

1999

Trehalases from a thermophilic fungus Thermomyces lanuginosus (M r 145 kDa) and a mesophilic fungus Neurospora crassa (M r 437 kDa) were purified to compare their thermal characteristics and kinetic constants. Both trehalases were maximally active at 50³C, had an acidic pH optimum and were glycoproteins (20% and 43%, w/w, carbohydrate content for T. lanuginosus and N. crassa, respectively). At their temperature optimum, their K m was similar (0.57 and 0.52 mM trehalose, for T. lanuginosus and N. crassa, respectively) but the V max of N. crassa enzyme was nine times higher than of T. lanuginosus enzyme. The catalytic efficiency, k cat /K m , for N. crassa trehalase was one order of magnitude higher (6.2U10 6 M 31 s 31 ) than of T. lanuginosus trehalase (4U10 5 M 31 s 31 ). At their T opt (50³C), trehalase from both sources exhibited similar thermostability (t 1a2 s 6 h). The energy of activation, E a , for T. lanuginosus trehalase was 15.12 kcal mol 31 and for N. crassa trehalase it was 9.62 kcal mol 31 . The activation energy for thermal inactivation for the N. crassa enzyme (92 kcal mol 31 ) was two-fold higher than for the T. lanuginosus enzyme (46 kcal mol 31 ). The present study shows that the trehalase of N. crassa is not only more stable but also a better catalyst than the T. lanuginosus enzyme. ß