scholarly journals The activities of pyruvate carboxylase, phosphoenolpyruvate carboxylase and fructose diphosphatase in muscles from vertebrates and invertebrates

1972 ◽  
Vol 130 (2) ◽  
pp. 391-396 ◽  
Author(s):  
B. Crabtree ◽  
S. J. Higgins ◽  
E. A. Newsholme
Keyword(s):  
Phosphoenolpyruvate Carboxylase ◽  
Pyruvate Carboxylase ◽  
Flight Muscle ◽  
Insect Flight ◽  
Tricarboxylic Acid Cycle ◽  
Mitochondrial Fraction ◽  
Bumble Bee ◽  
Insect Flight Muscle ◽  
Carboxylase Activity ◽  
Flight Muscles

1. The activities of pyruvate carboxylase, phosphoenolpyruvate carboxylase and fructose diphosphatase in crude homogenates of vertebrate and invertebrate muscles are reported. 2. Pyruvate carboxylase activity was present in all insect flight muscles that were investigated: in homogenates of bumble-bee flight muscle the activity was inhibited by ADP and activated by acetyl-CoA, and it was distributed mainly in the mitochondrial fraction. This is the first demonstration of pyruvate carboxylase activity in muscle. However, the activity appears to be restricted to insect flight muscle, since it was not found in other invertebrate or vertebrate muscles. 3. Since the three enzymes were never found together in the same muscle, it is concluded that these enzymes cannot provide a pathway for the synthesis of glycogen from lactate or pyruvate in muscle. Other roles for these enzymes in muscle are suggested. In particular, pyruvate carboxylase may be present in insect flight muscle for the provision of oxaloacetate to support the large increase in activity of the tricarboxylic acid cycle which occurs when an insect takes flight.

Preparation and Properties of the Contractile Element of Insect Fibrillar Muscle

1966 ◽  
Vol 1 (3) ◽  
pp. 311-330
Author(s):  
R. H. ABBOTT ◽  
R. A. CHAPLAIN
Keyword(s):  
Mechanical Performance ◽  
Flight Muscle ◽  
Insect Flight ◽  
Standard Procedure ◽  
Tween 80 ◽  
Mitochondrial Fraction ◽  
Enzymic Activity ◽  
Contractile Element ◽  
Insect Flight Muscle ◽  
And Function

Non-myofibrillar enzyme activities persist after glycerination of insect flight muscle. Preservation of mitochondrial structure and function in glycerol-extracted preparations complicates the study of direct effects on the myofibrillar contractile machinery. Non-myofibrillar adenosine triphosphatase and a significant amount of respiration and oxidative phosphorylation in the presence of added substrate persist in glycerol-extracted fibres of insect fibrillar muscle stored for 6 months at -18°C. The standard procedure used to extract actomyosin from myofibrils also extracts from the mitochondrial fraction a protein which shows the phenomenon of superprecipitation and undergoes viscosity changes in the presence of adenosine triphosphate and metal ions. Preparation of the true contractile structure of insect flight muscle therefore requires the removal of all non-myofibrillar activities. Reduction in the total number of mitochondria and of non-myofibrillar enzymic activity is achieved by treatment with the detergent Tween 80 subsequent to glycerination without impairing the mechanical performance of the fibres. This provides better experimental material for studies of the contractile system than the preparations commonly used. The fact that fibres can still perform oscillatory work after treatment with detergent and oligomycin confirms that the control mechanism for oscillation resides within the myofibrils.

scholarly journals Power and efficiency of insect flight muscle

1985 ◽  
Vol 115 (1) ◽  
pp. 293-304 ◽  
Author(s):  
C. P. Ellington
Keyword(s):  
Power Output ◽  
Flight Muscle ◽  
Insect Flight ◽  
Power Input ◽  
Mechanical Power ◽  
Insect Flight Muscle ◽  
Muscle Properties ◽  
System A ◽  
Mechanical Power Output ◽  
Flight Muscles

The efficiency and mechanical power output of insect flight muscle have been estimated from a study of hovering flight. The maximum power output, calculated from the muscle properties, is adequate for the aerodynamic power requirements. However, the power output is insufficient to oscillate the wing mass as well unless there is good elastic storage of the inertial energy, and this is consistent with reports of elastic components in the flight system. A comparison of the mechanical power output with the metabolic power input to the flight muscles suggests that the muscle efficiency is quite low: less than 10%.

A method for determining the periodicity of a troponin component in isolated insect flight muscle thin filaments by gold/Fab labelling

1992 ◽  
Vol 101 (3) ◽  
pp. 503-508
Author(s):  
R. Newman ◽  
G.W. Butcher ◽  
B. Bullard ◽  
K.R. Leonard
Keyword(s):  
Gold Particle ◽  
Colloidal Gold ◽  
Striated Muscle ◽  
Flight Muscle ◽  
Insect Flight ◽  
Insect Flight Muscle ◽  
Fab Fragment ◽  
Thin Filaments ◽  
Gold Particles ◽  
Almost All

Insect flight muscle has a large component (Tn-H) in the tropomyosin-troponin complex that is not present in vertebrate striated muscle thin filaments. Tn-H is shown by gold/Fab labelling to be present at regular intervals in insect flight muscle thin filaments. The Fab fragment of a monoclonal antibody to Tn-H was conjugated directly with colloidal gold and this probe used to label isolated thin filaments from the flight muscle of Lethocerus indicus (water bug). The distribution of gold particles seen in electron microscope images of negatively stained thin filaments was analysed to show that the probe bound to sites having a periodicity of approximately 40 nm, which is the expected value for the tropomyosin-troponin repeat. Conjugates of Fab with colloidal gold particles of 3 nm diameter labelled almost all sites. Conjugates with gold particles of 5 nm and 10 nm diameter labelled less efficiently (70% and 30%, respectively) but analysis of the distribution of inter-particle intervals among a number of filaments again gave the same fundamental spacing of 40 nm. The error in the measurements (standard deviation approximately +/− 4.2 for 5 nm gold/Fab) is less than earlier estimates for the size of the gold/Fab complex. Measurements on gold/Fab in negative stain suggest that the bound Fab contributes a shell about 2 nm in thickness around the gold particle. The radius of the probe (about 4.5 nm for 5 nm gold/Fab) would then be consistent with the value of error found. The size of the probe suggests that the gold particle binds to the side of the Fab molecule, rather close to the antibody combining site. The potential resolution of the technique may thus be better than originally expected.

X-ray titration of binding of β, γ-imido-ATP to myosin in insect flight muscle

Nature ◽  
1976 ◽  
Vol 262 (5569) ◽  
pp. 613-615 ◽  
Author(s):  
R. S. GOODY ◽  
J. BARRINGTON LEIGH ◽  
H. G. MANNHERZ ◽  
R. T. TREGEAR ◽  
G. ROSENBAUM
Keyword(s):  
Flight Muscle ◽  
Insect Flight ◽  
Insect Flight Muscle ◽  
X Ray
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